Page 2 of 243

Practical Geography for Secondary

Schools

GEOG

Mr. K. K. KIBBI

Publisher name

Page 2 of 243

Chapter ONE:

ELEMENTARY SURVEYING AND MAP

Specific Objectives: By the end of this topic, each student should be able to:-

i. Explain the meaning of simple land surveys without teacher’s

assistance

ii. Explain the types of simple land survey without teacher’s help

iii. Describe chain / tape survey without teacher’s assistance

iv. Explain different types of equipment used in chain/tap surveying

without teacher’s help

v. Practice chain/ tape surveying activities at school level

vi. Explain the importance of survey

INTRODUCTION

Students, we are going to start a course on surveying, cartography and

mapping. This course is an introduction to essentials and basic techniques

used in surveying, cartography and mapping. In this chapter, we are going

to discuss about basic concepts in surveying and levelling.

Meaning and types of survey

Surveying is the science and art for determining and recording the relative

positions of different objects (natural and manmade) on the surface of the

Earth by measuring the horizontal distances between them and by preparing

a map to any suitable scale. The practice of surveying is an art, because it is

dependent up on the skills, judgments and experience of surveyor. It may

also be considered as an applied science, because field and office

procedures rely upon a systematic body of knowledge. The process of

surveying involves measuring and recording distances, angles and heights of

the Earth’s surface features and drawing them on plan, section or map.

Survey as the act of viewing and examining the marking of maps, the

preparation of a body factual information is data collection tool used

together information about individuals. A survey may focus on factual

information about individuals, or it might aim to collect the opinions of the

survey takers.

Applicability of surveying

The two fundamental purposes for surveying are to determine the relative

positions of existing points and to mark the positions of new points on or

near the surface of the earth. However, different types of surveys require

different field procedures and varying degrees of precision for carrying out the

work.

Importance of Surveying

Surveying is one of the world’s oldest and most important arts because, as noted

previously, from the earliest times it has been necessary to mark boundaries and

divide land. Surveying has now become indispensable to our modern way of life.

The results of today’s surveys are being used to:

1. The Basic Engineering Discipline - Surveying is basic to all civil engineering

works. In transportation engineering, surveying provides the foundation and

continuity for route location, design, land acquisition, and all other

preliminary engineering. Surveys also set a basic "framework" of stakes,

which is used by contractors and engineers in building and inspecting

transportation projects.

2. The Thread of Continuity - Surveying is the single engineering function which

links all the phases of a project including conception, planning design, land

acquisition, construction and final monumentation.

3. Basis for Efficiency - To a great degree, the acceptability and cost-

effectiveness of planning, land acquisition, design, and construction are

dependent upon properly performed surveys.

Principles of Survey.

Whatever type of survey is being carried out, it will be governed by several

fundamental principles of survey, some of which we are to touch upon in this

chapter:

Control

The first principle is to establish a framework within which to work (“from the whole

to the part”). This is typically a system of control stations, positioned to a high

degree of accuracy. Surveys between these control points can then be carried out

by less elaborate methods. Any errors, which then arise, are contained within the

framework of the control points and can be adjusted to it. Errors will therefore be

restricted in magnitude and will not be allowed to accumulate throughout the whole

survey. Traditionally, this has generally been achieved by starting with a very rigid

framework of primary triangulation, which is broken down by second and third order

networks. As previously mentioned, the framework is more likely to be fixed by GPS

these days.

Checking

The second principle is that all survey work must be checked. Using good survey

procedures will ensure that many operations are self-checking, but when this is not

possible independent checks should be applied before the survey is completed.

Economy of Accuracy

Economy of accuracy means that the standards of accuracy should be proportionate

to the needs of the task and no higher. For example Great Britain has been divided

by Ordnance Survey into urban, rural and mountain/moorland areas, and

appropriate accuracy standards have been set for each area. An accuracy greater

than that of the control used cannot be achieved. Also, the higher the accuracy, the

higher the cost. The 1:1250 scale accuracy appropriate for urban areas would be

very expensive to achieve in all areas – but more importantly, it would not be

required.

Consistency of Accuracy

The same standards should be maintained for each stage of the task. This applies

not only to the accuracy, but also to the quality of the control used and to the

density of control or detail points provided. In the case of Ordnance Survey

consistency is achieved by having sets of rules and guidelines, a specification for

the data, and quality systems for data capture, maintenance, and the creation of

the final data products.

Revision

If it is at all possible, any requirements for future revision should be allowed for

when planning a survey scheme. When traversing was used by Ordnance Survey as

the primary means of providing “minor control” i.e. accurately positioned control

stations from which features could be captured, stations had to be sufficiently

permanent and well positioned to be useful in the future. With the use of GPS now

this principle is still relevant, for example, in timing the survey of large housing

estates, to obtain maximum benefit without several repeat visits.

Safeguarding

If permanent stations have been sited, they will be of no use in the future if they

cannot be found. The station mark should be as permanent as possible. The mark

needs to be found in the future, so some sort of documentation will be required. The

station will need a reference number, its exact position recorded and a dimensioned

location diagram. Ideally such records will be updated and amended as necessary.

This is still relevant today for Ordnance Survey although only for the network of GPS

fixed control stations rather than the thousands of minor control stations which

once needed to be maintained.

Types of survey

There are two types of surveying depending on the area, the nature of the terrain

and the amount and the distribution of the information needed namely; aerial

surveying and ground surveying. Aerial surveying is used to recording information

quickly on large areas and make measurements through using airplane. Ground

surveying is applied where aerial photograph interpretation is difficult and when

detailed information is required. Ground surveying is further categorized into

geodetic surveying and plane surveying.

Geodetic Surveying

Geodetic survey refers to the ground or land survey which considers the curvature

of the Earth surface. Basically it deals with large distance measurements on the

Earth surface. It provide survey stations located on large distance apart, determine

earth curvature distances, shape, size and gravity measurement on the Earth.

Geodetic surveys are carried at national level and often involve international

cooperation. Geodetic surveying is carried under the discipline called Geodesy in

which the size and shape of the earth are examined. Geodetic surveying is

undertaken for the purpose of determining positions of points on the Earth surface

which serves as control points for all other surveys.

Plane Surveying

In plane surveying, we usually measure horizontal linear distances between two

points and angles between two lines. The linear measurement of distance between

two points on the earth’s surface can be carried out by several methods depending

upon the degree of accuracy and precision required. Plane surveying refers to the

type of the ground survey which do not take into consideration the curvature of the

Earth. We know that, the shape of the Earth is spheroidal. Thus, the surface is

obviously curved. However in plane survey the curvature of the Earth is not taken

into consideration. This is because plane surveying is carried out over a small area.

So, the surface of the Earth is considered as plane (flat). In such surveying a line

joining any two points is considered to be straight. It involves measurements on

relatively small areas. The points on the Earth are projected upon a horizontal

surface (a plan), and angular measurement used are horizontal. The actual

measurement done by plane surveying represents measurement of the horizontal

plane rather than the rugged Earth surface measurement. Plane surveying is done

for the one of the following purpose;

a. Determining horizontal distance between two or more points on the

land surface.

b. Locating physical and non-physical features on the land surface.

c. Locating direction of various features on the land surface

d. Determining area of a given piece of land.

In plane surveying horizontal lines are assumed to be straight line and all vertical

lines are parallel.

Figure. In plane surveying, the curvature of the earth is neglected, and

Vertical distances are measured with reference of a flat plane.

UNDERSTANDING SURVEY MISTAKE, ERROR, ACCURACY AND PRECISION IN

SURVEYING.

No measurement can be perfect or exact because of the physical limitations of the

measuring instrument as well as limits in human perception. The difference

between a measured distance or angle and its true value may be due to mistakes

and /or errors. These are two distinct terms. It is necessary to eliminate all mistakes

and to minimize all errors when conducting a survey of any type.

BLUNDERS: A blunder is a significant mistake caused by human errors. It may also

be called a gross error. These are mistakes that can be attributed to the

inexperience of the team leaders. They include discontinuing the chain length (e.g.

where some arrows are misplaced); misreading of the tape; reading tape upside

down (e.g. taking 6 to be 9), etc. By taking the necessary precautions, these errors

can be corrected. Generally, it is due to the inattention or carelessness of the

surveyor and it usually results in a large difference between the observed or

recorded quantity and the actual or the true value.

Mistakes may be caused by sighting on a wrong target with the transit when

measuring an angle, a by tapping to an incorrect station. They also may be caused

by omitting a vital piece of information, such as the fact that a certain

measurement was made on a steep slope instead of horizontally. The possibilities

for mistakes are almost endless. However, they are only caused by occasional

lapses of attention.

ERRORS: An error is the difference between a measured quantity and its true

value, caused by imperfection in the measuring instrument, by the method of

measurement, by natural factors such as temperature, or by random variation in

human observation. It is not a mistake due to carelessness. Errors can never be

completely eliminated, but they can be minimized by using certain instruments and

field procedures and by applying computed correction factors. Surveyors, whose

work must be performed to exacting standards, should therefore thoroughly

understand the different kinds of errors, their sources and expected magnitudes

under varying conditions, and their manner of propagation. Only then can they

select instruments and procedures necessary to reduce error sizes to within

tolerable limits. The errors can be divided into two groups as a cumulative

(systematic) errors; and compensating (accidental) errors;

Cumulative Errors:

These are repetitive errors that are caused by imperfections in the surveying

equipment, by the specific method of observation, or by certain environmental

errors or cumulative errors. Cumulative errors are said to be systematic errors as

they are one-directional hence keep on accumulating as the survey progresses. If

not checked they have serious implications to the accuracy of the survey. Errors in

this include incorrect length of the tape, or the tape not being in line. Since the

sources of these errors are known, they can be eliminated. They can either be

positive or negative errors. While positive errors shorten the measurement (e.g.

where the tape length is shorter than what it should be) while negative errors

elongates the measurements (e.g. where the tape is longer than what it should be).

Checking the equipment can eliminate these errors.

Under the same conditions of measurement, systematic errors are constant in

magnitude and direction or sign (either plus or minus). They usually have no

tendency to cancel if corrections are not made.

For example, suppose that a 30-m steel tape is the correct length at 200c and that

it is used in a survey when the outdoor air temperature is, say 350c. Since steel

expands with increase in temperatures, the tape will actually be longer than it was

at 200c. And also transits, theodolites and even EDM are also subjected to

systematic errors. The horizontal axis of rotation of the transit, for instance, may

not be exactly perpendicular to the vertical axis.

Compensating Errors:

An accidental or random error is the difference between a true quantity and a

measurement of that quantity that is free from blunders or systematic errors.

Accidental errors always occur in every measurement. They are the relatively small,

unavoidable errors in observation that are generally beyond the control of the

surveyor. These random errors, as the name implies, are not constant in magnitude

or direction. Compensating errors are said to be accidental errors hence cancel out

and does not pose serious problem to the accuracy of the survey. They arise as a

result of not being perfect in the use of the equipment or in the whole survey

process.

One example of a source of accidental errors is the slight motion of a plumb bob

string, which occurs when using a tape to measure a distance. The tape is generally

held above the ground, and the plumb bob is used to transfer the measurement

from the ground to the tape. The effect can either be positive or negative.

If two or more measurements of the same quantity are made, random errors usually

cause different values to be obtained.

As long as each measurement is equally reliable, the average value of the different

measurements is taken to be the true or the most probable value. The average (the

arithmetic mean) is computed simply by summing all the individual measurements

and then dividing the sum by the number of measurements.

Using appropriate statistical formulas, it is possible to test and determine the

probability of different ranges of random errors occurring for a variety of surveying

instruments and procedures. The most probable error is that which has an equal

chance (50 percent) of either being exceeded or not being exceeded in a particular

measurement. It is sometimes designated as E90.

In surveying, the 90 percent error is a useful criterion for rating surveying methods.

For example, suppose a distance of 100.00 ft is measured. If it is said that the 90

percent error in one taping operation, using a 100 ft tape, is ± 0.01 ft, it means that

the likelihood is 90 percent that the actual distance is within the range of 100.00 ±

0.01 ft. Likewise, there will remain a 10 percent chance that the error will exceed

0.01 ft. It is sometimes called maximum anticipated errors. The 90 percent error

can be estimated from surveying data, using the following formula from statistics.

E90 = 1.645 × √ [Σ (Δ) 2/ (n (n-1))]

Where: Σ = sigma, “the sum of”

Δ = Delta, the difference between each individual measurement

and the average of n measurements.

n = the number of measurements.

For example, if we have measured the distance, through using the tape several times; for nine separate measurements of 900ft distance, each with a maximum probable error of ± 0.01 ft. It is tempting simply to say that the total error will be 9× (±0.01) = ± 0.09 ft. But this would be incorrect. Since some of the errors would be plus or some would be minus, they would tend to cancel each other out. Of course, it would be very unlikely that errors would completely cancel, and so there still be a remaining error at 900 ft.

A fundamental property of accidental or random errors is that they tend to accumulate, or add up, in proportion to the square root of the number of measurements in which they occur. This relationship, called the law of compensation, can be expressed mathematically in the following equations:

E = E1× √n

Where E = the total error in n measurements.

E1 = the error for one measurement.

n= the number of measurements.

From the above example, E = ± 0.01√9 = ± 0.01 × 3 = ± 0.03 ft.

In other word, we can expect the total accidental error when measuring a distance

of 900 ft to be within a range of ± 0.030 ft, with a confidence of 90 percent. It must

be kept in mind that this type of analysis assumes that the series of measurements

are made with the same instruments and procedures as for the single measurement

for which the maximum probable error is known.

Accuracy and Precision in surveyingAccuracy and precision are two distinctly different terms, which are of importance in

surveying. Surveying measurements must be made with an appropriate degree of

precision in order to provide a suitable level of accuracy for the problem at hand.

Since no measurement is perfect, the quality of result obtained must be

characterized by some numerical standard of accuracy.

Accuracy refers to the degree of perfection obtained in the measurement or how

close the measurement is to the true value. When the accuracy of a survey is to be

improved or increased, we say that greater precision must be used.

Precision refers to the degree of perfection used in the instruments, methods, and

observations- in other word, to the level of refinement and care of the survey. In

summary:

Precision – Degree of perfection used in the survey.

Accuracy – Degree of perfection obtained in the results

In a series of independent measurements of the same quantity, the closer each

measurement is to the average value, the better is the precision. High precision is

costly but is generally necessary for high accuracy. The essential art of surveying is

the ability to obtain the data required, with a specific degree of accuracy, at the

lowest cost. The specified degree of accuracy depends on the type and the purpose

of the survey.

Illustration of accuracy and precision

In the following example, the more precise method (steel tape) resulted in the more

accurate measurement.

“True”

Distance

Measured

Distance

Error

Cloth tape 157.22 157.2 0.02

Steel tape 157.22 157.23 0.01

However, it is conceivable that more precise method can result in less accurate

answers. But if the steel tape had previously been broken and in correctly repaired,

the result would still be relatively precise but very inaccurate.

Error of Closure

The difference between a measured quantity and its true value is called error of

closure. In some cases, the closure can be taken simply as the difference between

two independent measurements.

For example, suppose a distance from point A to point B is first determined to be

123.25 m. The line is measured a second time, perhaps from B to A, using the same

instrument and methods. A distance of 123.19 m is obtained. The error of closure is

simply 123.25 – 123.19 = 0.06m. It is due to accidental errors, as long as blunders

have been eliminated and systematic errors corrected.

Relative Accuracy

For horizontal distances, the ratio of the error of closure to the actual distance is

called the relative accuracy. Relative accuracy is generally expressed as a ratio with

unity as the first number of numerator. For example, if a distance of 500 ft were

measured with a closure of 0.25 ft, we can say that the relative accuracy of that

particular survey is 0.25/500, or 1/2000. This is also written as 1:2000. This means

basically that for every 2000 ft measured, there is an error of 1 ft. The relative

accuracy of a survey can be compared with a specified allowable standard of

accuracy in order to determine whether the results of the survey are acceptable.

Relative accuracy can be computed from the following formula:

Relative accuracy = 1: D/C, where D = distance measured and C = error of

closure.

Example. A group of surveying students measure a distance twice, obtaining 67.455

and 67.350 m. What is the relative accuracy of the measurements?

Example2. Determine the accuracy of the following, and name the order of accuracy

with reference to the US standards summarized.

Error, m Distance, m8.0 305600.07 20001.32 84600.13 17091.0 175430.72 1800

UNDERSTAND THE CLASSIFICATION OF SURVEYING:

Although in this book we are going to discuss in detail four methods of surveying

includes chain or tape surveying, prismatic or traversing compass survey, plane

table surveying and levelling. But for easy understanding of surveying and the

various components of the subject, we need a deep understanding of the various

ways of classifying it. Surveying is classified based on various criteria including the

instruments used, purpose, the area surveyed and the method used.

Classification of surveying based on the surface and the area surveyed include land

survey, marine or hydrographic survey and astronomical survey.

Land survey: It is also called property survey or boundary survey. It is performed in

order to establish the positions of boundary lines and property corners. It is usually

performed whenever land ownership is to be transferred or when a large tract of

land is to be subdivided in to smaller parcels for development. It is also performed

before the design and construction of any public/private land-use project. Land

surveys are done for objects on the surface of the earth. It can be subdivided into:

a. Topographic surveys: These are surveys where the physical features of the

earth such as hills, valleys, mountains, rivers, roads, houses, and settlements

on the surface of the earth are measured, and maps and plans prepared to

show their relative positions both horizontally and vertically. Depending on

the extent of the survey these may be either geodetic type surveys or plane

surveys, where no account is taken of the earth’s curvature. The data’s

obtained from a topographic surveys are plotted in a map called topographic

map and the shape of the ground is shown with lines of equal elevation called

contours.

b. Cadastral or property survey is used to determining property boundaries

including those of fields, houses, plots of land, etc. Cadastral surveys are

usually undertaken to define and record the boundaries of properties,

legislative areas and even countries. In many cases cadastral surveys will be

almost entirely topographic, with features defining boundaries. This survey

tends to be relatively precise with the coordinate positions and nature of the

boundary defining features recorded as part of the survey. Again geodetic

principles may have to be applied in the case of country boundaries, but

much of the work consists of plane surveying.

c. City surveys: The surveys involving the construction and development of

tows including roads, drainage, water supply, sewage street network are

generally referred to as city survey.

Marine or Hydrographic Survey: Those are surveys of large water bodies for

navigation, tidal monitoring, the construction of harbours etc. The taking of

soundings on shares aid banks aid the determination of water depths helps in the

production of topographic maps and the survey of batty – metric controls.

Astronomical Survey: Astronomical survey uses the observations of the heavenly

bodies (sun, moon, stars etc) to fix the absolute locations of places and gratiscules

(lines of longitude and (attitude) on the surface of the earth.

Some times survey is conducted in order to serve certain purposes in society. So

basing on the purposes survey can be classified as;-

a. Engineering or site survey: Engineering or site survey is used to acquire the

required data for the planning, design and execution of engineering projects

like roads, bridges, canals, dame, railways, buildings, etc. These are surveys

undertaken to provide information for construction projects. They are

generally large-scale topographic surveys and usually plane surveys except

on very large construction projects.

b. Control Survey: Control Survey uses geodetic methods to establish widely

spaced vertical and horizontal control points. Control survey is of the two

kinds including horizontal and vertical:

i. Horizontal control survey: The surveyor, using temporary/permanent

markers, places several points in the ground. These points, called

stations, are arranged throughout the site area under study so that it

can be easily seen. The relative horizontal positions of these points are

established, usually with a very high degree of precisions and

accuracy; this is done using transverse, triangulation or trilateration

methods.

ii. Vertical control survey: The elevations of relatively permanent

reference points are determined by precise leveling methods. Marked

points of known elevations are called elevation benchmarks. The

network of stations and benchmarks provide a framework for

horizontal and vertical control, up on which less accurate surveys can

be based.

c. Geological Survey: Geological survey is used to determine the structure and

arrangement of rock strata. Generally, it enables surveyors to know the

composition of the earth’s constituents.

d. Military or Defense Survey: Military or Defense Survey is carried out to map

places of military and strategic importance

e. Archeological survey: Archeological survey is carried out to discover and map

ancient/relies of antiquity.

In conducting survey some methods involve so as to obtain the reliable data.

Methods like triangulation and traversing or offset are popular used during

surveying. So basing on the methods survey can be Classified as;-

a. Triangulation Survey: In order to make the survey, manageable, the area to

be surveyed is first covered with series of triangles. Lines re first run round

the perimeter of the plot, then the details fixed in relation to the established

lines. This process is called triangulation. The triangle is preferred as it is the

only shape that can completely over an irregularly shaped area with

minimum space left.

b. Traverse or offset survey: If the bearing and distance of a place of a known

point is known it is possible to establish the position of that point on the

ground. From this point, the bearing and distances of other surrounding

points may be established. In the process, positions of points linked with

lines linking them emerge. The process of establishing these lines, while the

connecting lines joining two points on the ground is called traversing. Joining

two lines while bearing and distance is known as traverse. A traverse station

is each of the points of the traverse, while the traverse leg is the straight line

between consecutive stations.

Lastly, the proper instruments should be considered during surveying. Surveyors

must have enough and explicitly knowledge on the instruments to be used before

conducting any survey. So survey can be classified basing on instruments as;-

a. Chain or Tape Survey: This is the simple method of taking the linear

measurement using a chain or tape with no angular measurements made.

b. Compass Survey: Here horizontal angular measurements are made using

magnetic compass with the linear measurements made using the chain or

tape.

c. Plane table survey: This is a quick survey carried out in the held with the

measurements and drawings made at the same time using a plane table.

d. Theodolite survey: This is the measurement and mapping of the relative

heights of points on the earth’s surface showing them in maps, plane and

charts as vertical sections or with conventional symbols. It takes vertical and

horizontal angles in order to establish controls. It is also, called levelling.

1. CHAIN OR TAPE SURVEYING

Introduction

This is the simplest form of survey where only the linear measurements are made

while the angular, measurements are ignored. This type of surveying is suitable for

surveys of small extent on open ground to secure data for exact description of the

boundaries of piece of land or to take simple details. The principle of chain survey

or chain triangulation, as is sometimes called is to provide a skeleton or framework

consisting of a number of connected triangles, as triangle is the only simple figure

that can be plotted from the lengths of its sides measured in the field. To get good

results in plotting, the framework should consist of triangles which are as nearly

equilateral as possible. Chain survey is carried out to obtain data further accurate

description of property boundaries; to prepare an accurate plan of a plot of law and

determine its area; to delineate the boundary of a piece of land in a previously

surveyed location; to share a piece of land into smaller units; to obtain data for

engineering project (e.g. road and rail alignment). The chain survey is preferred

when the ground is nearly flat and open (avoiding crowded areas with many details,

or areas which are heavily wooded or undulating) and also when the area to be

surveyed is smaller and it is not suitable for large areas that are crowded with many

details and wooded and undulating areas.

ADVANTAGES AND DISADVANTAGES OF CHAIN SURVEY

Advantages

Disadvantages

TECHNICAL TERMS IN CHAIN SURVEY

Station points:

Main Stations: Main stations are the end of the lines, which command the

boundaries of the survey, and the lines joining the main stations re called the main

survey line or the chain lines.

Subsidiary or the tie stations: Subsidiary or the tie stations are the point selected on

the main survey lines, where it is necessary to locate the interior detail such as

fences, hedges, building etc. Survey lines include;

Tie or subsidiary lines: A tie line joints two fixed points on the main survey lines. It

helps to checking the accuracy of surveying and to locate the interior details. The

position of each tie line should be close to some features, such as paths, building

etc.

Chain line:

Check Line: A check line also termed as a proof line is a line joining the apex of a

triangle to some fixed points on any two sides of a triangle. A check line is

measured to check the accuracy of the framework. The length of a check line, as

measured on the ground should agree with its length on the plan.

Base Lines: It is main and longest line, which passes approximately through the

center of the field. All the other measurements to show the details of the work are

taken with respect of this line.

Offsets: These are the lateral measurements from the base line to fix the positions

of the different objects of the work with respect to base line. These are generally set

at right angle offsets. It can also be drawn with the help of a tape. There are two

kinds of offsets:

Perpendicular offsets: The measurements are taken at right angle to the survey line

called perpendicular or right angled offsets.

Oblique offsets: The measurements which are not made at right angles to the

survey line are called oblique offsets or tie line offsets.

PRINCIPLES OF CHAIN SURVEYING

The principle of chain surveying is derived from principle of triangulation. The whole

area to be surveyed is divided into framework of triangles of suitable sizes. Network

of triangles is selected as these are simple geometrical figures which can be easily

plotted with the measurements of its sides only. It is advisable to use well-

conditioned triangles whose sides are as nearly equal as possible with angles

between 30o to 120o. This shaping of triangles result in higher accuracy. The

triangulation of area avoids the need of measuring angles hence can be surveyed

and plotted easily by measuring distances by changing alone.

PROCESSES OR PROCEDURES OF CHAIN SURVEY

The chain survey processes or procedures follow the steps which includes:-

Reconnaissance survey, measurement and Field work, and Office work. The

procedure will be explained under the following headings: Reconnaissance,

Ranging, Running of a chain line, Measurement of offset and Booking drying

chaining:

Reconnaissance Survey: This is a pre-field work and measurement phase. It requires

taking an overall inspection of the area to be surveyed to obtain a general picture

before commencement of any serious survey. Walking through the site enables one

understand the terrain and helps in determining the survey method to be adopted.

The initial information obtained in this stage helps in the successful planning and

execution of the survey. The scale is determined by getting an estimate of the

maximum dimensions of the area by pacing and measurements.

Measurement and Field work

This is the actual measurements in the field and the recordings in the field

notebook. To get the best results in the field, the surveyor must be acquainted

(familiar) with the functions of the equipment and take good care of them. Also, the

surveyor must ensure the required equipment are full available in order to perform

the following activities

Ranging: Ranging involves placing ranging poles along the route to be measures so

as to get a straight line. The poles are used to mark the stations and in between the

stations.

Running a chain line: for effectively running a chain line, surveyor takes a number

of arrows and holding the handle of the tape, the leader starts the chaining process

by walking along the line towards the end of the line learning behind the follower

holding the tape, with signals from the follower, the leader extends the tape along

the line, and places an arrow where the tape ends. The procedure is continued until

the whole line is coursed.

Measurement of offsets: To measure, two team leaders called a leader and a

follower are chosen. As the chaining progresses, the leader leaves the tape on the

ground for the offset and booking teams to do their work. Offsets are measurements

made outside the main survey line. Where the appropriate equipment are not

available, a simple method of taking measurements along the survey line at two

points to the object is used.

Booking: Booking refers to process of entering the surveyed measurements in the

field note book. In order to avoid confusion after the measurements in field, booker

or recorder must take care to record neatly results in a field notebook. Booking that

takes measurement is done along the line from the bottom of the page to the top.

Right and left entries on the page is made to correspond with the right and left

measurements on the ground. It is advisable that each chain line should be

recorded in a separate page.

EQUIPMENT USED IN CHAIN SURVEYING:

Although, survey equipment can be divided into three, namely (i) Those used for

linear measurement (E.g. Chain, steel band, linear tape)(ii) Those used for slope

angle measurement and for measuring right angle (E.g. Abney level, clinomater,

cross staff, optical squares) (iii) Other items (E.g. Ranging rods or poles, arrows,

pegs etc). Chain survey is mainly concerned with the measurement of distances

hence the main equipment used include the following:

Chain

A chain is made up of steel or iron pieces of wire known as links which are joined

together with circular or oval rings that make for flexibility. It has a brass handle at

both ends which is part and parcel of the total length of the chain known as chain

length. Different kinds of chains exist including Gunter’s chain, Engineers chain and

metric chains. The basic instrument or equipment used in chain surveying is a chain

or a tape. A survey chain is generally composed of 100 or 150 links formed by

pieces of galvanized mild steel wire of 4 mm diameter and has a brass tag at every

10th link called a teller. The ends of each link are looped and connected together by

means of three circular or oval shaped wire rings to provide flexibility to chain. The

length of each link is measured as the distance between the centers of two

consecutive middle rings. The joints of links are welded to avoid length changes due

to stretching.

The ends of chain are provided with brass handles with swivel joints. This helps in

turning the chain without twisting. The end link length includes the length of handle

and is measured from the outside of the handle, which is considered as zero point

or the chain end. Tallies, which are metallic tags of different patterns, are provided

at suitably specified points in the chain to facilitate quick and easy reading. A semi-

circular grove is provided in the center on the outer periphery of handle of chain for

fixing the mild steel arrow at the end of one chain length.

The number of links in a chain could be 100 in a 20 m chain and 150 in a 30 m

chain. The details of a metric chain are as shown in Figure 2.1.

Figure 1.1: Chain

The chain can be used conveniently in a rugged terrain and can be subjected to

rough use under adverse site conditions. It can be read easily by even semi-literate

persons. However, the length is liable to be changed due to continued usage. Its

comparatively heavy weight may cause sagging in the chain thereby affecting the

measurement accuracy.

Tape

Tapes have replaced chains in recent years because they are light, portable and

flexible. The tape is made from steel strap or fibber band with length of 10 m, 20 m,

or 30 m. Graduated in 10 mm division and numbered at each 100 mm (10 cm)

division. Tapes can be used for more accurate measurements of lengths. They are

lighter and easier to handle and comparatively less liable to change in length than

chain. Different types of tapes exist and they are classified according to the

materials they are made of hence we have cloth or line tape, metallic tape, steel

tape and in car take: Depending on the material, these can be of following types:

Cloth or linen tapes

These are made of linen cloths that are varnished to resist moisture. Cloth or linen

tapes are 12 to 15 mm wide closely woven linen varnished for moisture proofing.

These are available in range varying from 2 m to 50 m in lengths in such a way that

tapes of 10 m, 20 m, and 30 m are commonly available. Since these are liable to

shrink when wet and alter in length due to twisting or stretching, these are rarely

used for accurate measurements. The main limitation of cloth tape is that it

stretching of the length can introduce errors in measurements. It is not as heavy

and strong as chain or steel tape hence is likely to twist and tangle and does not

remain straight in strong winds. So, the better ones are interwoven with small

brass, copper or bronze wires to provide strength and resistance to shrinkage and

stretching.

Steel tapes

These are fine steel ribbons used to provide measurement of superior accuracy than

cloth or metallic tapes. With a ring at the end, whose length is included in the

length of the tape, steel tapes consist of light strip of steel with width ranging from

6 to 10 mm, in lengths of 2 to 50 m.

Steel tapes can be more accurately graduated. The graduations are etched (fixed)

as meters, decimeters and centimeters on one side and 0.2 m links on other side.

The steel tapes are very delicate and hence not suitable for rough usage. These also

require frequent cleaning and drying to avoid rusting. It is also difficult to read as

compared to chain.

Figure 1.12: Steel Tape

Metallic Tape

These are more durable than cloth tapes as they are made up of cloth that are

reinforced with brass or copper wires. Usually, between 20 to 30m, they come in a

leather cases with winding mechanism.

Figure1.13: Metallic tapes

Invar tapes

Invar tapes made up of alloy of Nickel (36%) and steel can be used for higher

accuracy as their coefficient of thermal expansion is very low. However, it is costly

and more delicate in use.

Figure1.14: Invar tapes

Fiberglass tapes

In recent times, fiberglass tapes are extensively used in the field survey because of

its low thermal expansion, cheapness, strength, ruggedness and durability. These

are available in ranges varying from 5 m to 30 m in length. This is used primarily to

obtain a high degree of precision, invar tapes are more expensive and softer than

steel tapes.

Figure 1.15: Fiberglass Tape.

Steel Bands:

Steel bands made up of ribbon of steel with brass swivel handle at each end. Also

called a band chain. The steel band’s width is usually 16 mm and length of 20 or 30

m. The steel band is used to obtain accurate measurements, it is lighter to handle

than the chain, and its length is not stretched due to usage. Band is normally

divided by brass studs at every 20 cm and numbered at every one meter. The steel

bands are very delicate and hence not suitable for rough usage. These also require

frequent cleaning and drying to avoid rusting.

Figure 1.16:

Steel Bands:

Surveyor’s band

Surveyor’s band is made of steel

strip which is rolled in metal

frame with winding handle. The

lengths of surveyor’s

band can be of 30 m, 50 m and

100 m.

Figure 1.17: Surveyor’s band

Optical Squares

This is an optical instrument used to take offsets at right angles from the chain

lines. Offsets are measurements made from outside the survey line of triangulation

or traverse skeleton to a property boundary or fence or wall offsets enable one fix

point details in relation to the chain line.

Figure1.121: Optic squares

Cross staff

This is a simple form of optical squares used for the same purpose of fixing offsets.

Constructed in the form of a wind vane, consisting of a cross with vertical ends with

slits. Offsets are taken using the lines of sight which cross at right angles. Cross

staff is made of wood or metal with eye slits at right angle.

Figure 1.18: Cross staff

Arrow or chain pin

An arrow is a piece of steel skewer and iron bent at the top into a circle and with a

posited end allow for easy penetration into the ground when chaining a long line. It

is used primarily for marking the end of chaining and temporary stations. Arrows

should be colored rag or tag tied to the circular end to make them more visible.

Arrows or chain pins, as these are called sometime, are made of stout steel wire 4

mm in diameter, 400 to 450 mm long and black enameled. The chain has to be laid

down a number of times and the positions of the ends are marked with arrows. If

arrows are not available pegs can be used to mark temporary stations on the

ground.

Figure 1.19: a) Chaining pin (b) Keel

Ranging pole

This is a pole of about 2 meters in length alternatively painted white and red and is

pointed at one end so that can be seen easily from distance. It colored in white,

black and red at equal distance. They are used to mark stations and for ranging (is

getting out straight lines). To do this two poles are fixed at the 2 stations or points

and this enables one to measure along straight lines by placing a series of ranging

poles along the route in order to get the straight lines.

Figure 1.120: surveyor’s Range pole

Flagpole or flag staff

This is a surveying instrument consisting of a straight rod painted in bands of

alternate red and white each one foot wide; used for sightings by surveyors. A pole

on which a flag is raised. Also called flagstaff. Flagpole is a staff or pole on which a

flag is or can be displayed so that, to announce as a test to gauge reactions.

Figure 1.122: Flag pole

Wooden Pegs

These are made of stout timber generally 25 to 30 mm square or circular size and

150 mm long as shown in Figure 1.6. Wooden pegs are normally used to mark

station position on ground on a quasi-permanent state. These are tapered at one

end so that they can be driven in the ground easily.

Figure 1.123: Wooden pegs

Plumb Bob

It is usually heavy spherical or conical ball, as shown in Figure 1.124, of metal and is

used to transfer points on ground by suspending it with the help of a strong thread.

It is used in measuring distances on sloping ground by stepping. With a plumb bob

surveyor can check if the ranging pole is vertical. Compass, Dumpy levels and

Theodolites are also positioned over the station point accurately with the help of

plumb bobs.

Figure 1.124: Plumb Bob

Line Ranger

A line ranger consists of either two plane mirrors or two right angled isosceles

prisms placed one above the other as depicted in Figure. The diagonals of both

the prisms are silvered so as to reflect the incident rays. Line rangers are

provided with a handle to hold the instrument. A line ranger can also be used to

draw offset on a chain line.

Figure1.125 Line Ranger

Field Note book and pencil

Figure 1.127 Note book and pencil

RULES FOR FIELD NOTES

1. Record all field data carefully in a field book at the moment they are

determined.

2. All data should be checked at the time they are recorded.

3. An incorrect entry of measured data should be neatly lined out, the correct

number entered next to or above it.

4. Field notes should not be altered, and even data that are crossed out should

still remain legible.

5. Original field records should never be destroyed, even if they are copied for

one reason to another.

6. A well-sharpened medium-hard pencil should be used for all field notes.

7. Sketches should be clearly labeled.

8. Show the word VOID on the top of pages that, for one reason or another, are

invalid.

9. The field note book should contain the name, address, and the phone

number.

10.Each new survey should begin on a new page.

11.For each day of work, the project name, location, and date should be

recorded in the upper corner of the right –hand page.

PRACTICAL INSTRUCTIONS FOR CHAIN SURVEYING

1. Preliminary Inspection

1. Walk over the whole area to be surveyed and note good line of sight, corners

and intersections that can be seen from where you are standing.

2. Choose the main triangles with at least two sides running close to the outside

boundary of the area to be surveyed.

3. Build up the secondary triangles with their sides intersecting sharply.

4. Draw a key diagram of the lines you are going to use, lettering or numbering

the stations you are going to use. See figure 1.129. In the fig. below the

surveyor need to measure a line between two existing buildings, which is

close to the new fence feature to be surveyed. The line has been “tied out” at

41.8m. Offsets are raised at right angles to measure line to each corner on

the new feature and to selected points on the curved section. The length of

each offset is measured and then booked.

6.9 6.9

Figure 1.129: Sketch plan of the area to be surveyed

2. Running the Chain Lines

a. Chain lines are run by surveyor team that comprises a leader, a follower and

booker. The leader starts off from the beginning of the line, holding the front

end of the chain and taking with him a number of arrows and ranging poles.

When the chain is full stretched the follower at the starting point of the line

signals the leader left or right until the end of the chain is in direct line with

the station at which the leader is standing.

b. The follower erects a ranging pole at the first base point and sights in the

leader’s pole by signal.

c. The leader straightens the chain and drives in a skewer or an arrow at the

exact point.

d. The chain is left on the ground while offset and tie lines are measured.

41.8

New fence to be surveyed

4.44.4

0.00.0

6.3

14.714.

8.2

24.224.

5.55.

35.035.

e. The leader then takes his end of the chain further along the line and the

follower comes up to the skewer.

f. The same process is repeated until the line is completed

3. Measuring Offsets and Tie Lines

a. Some of the outside boundaries of the areas consist of curved edges whose

position must be fixed by taking offsets.

b. Offsets points e.g. curved edges points are fixed by locating the right angle

line to a point using a cross staff.

c. If the distance to objects or other details to be included are quite long tie

lines should be used.

d. Tie lines are used to measure distance to a point from two points on the

chain line

e. For example a building is fixed by making two measurements towards each

of the near corners. The building is then measured.

4. Booking the surveyed measurements in the field note book.

Definition of booking

Types of booking method in chain survey

BOOKING METHODS AND TECHNIQUES (PROCEDURES) IN CHAIN SURVEY

Although today most measurements are keyed directly into PRISM software by

Ordnance Survey surveyors, when using non-electronic methods the technique used

for booking measurements made during detail survey goes back to that used in the

days of chain survey. Most surveyors adhere to basic rules which then enable other

surveyors to understand what has been recorded. This is useful as it allows an

independent check of the work, or completion of a task by a different surveyor.

Clarity and accuracy of booking are obviously essential. Although neatness is

desirable, mistakes inevitably occur and should be cancelled and amended in the

field. The rewriting of bookings in the office should be avoided wherever possible as

this can lead to mistakes, which may go undetected. Traditionally, measurements

along a taped line are normally recorded within two parallel lines ruled down the

center of the page. Distances along the line are be entered from the bottom of the

page and proceed sequentially. Detail “picked-up” along the line either as an offset,

straight, reference or in-direction measurement etc. should be sketched on the

correct side of the parallel line in its approximate position relative to other detail.

Distances recorded to this detail should be positioned on the booking sheet to avoid

ambiguity. For lines, which have been tied out, the total length of the line is entered

at the top of the page and is under and over scored. Chain survey must be free from

mistakes or blunders. A potential source of major mistakes in surveying practice is

the careless or improper recording of field notes. The art of eliminating blunders is

one of the most important elements in surveying practice. In order for the surveyor

to eliminate mistakes or blunders, clear and neat booking must be put into

consideration. The following are booking techniques or procedures surveyor must

follow in order to ensure good booking.

a) Draw two parallel lines about 20 mm apart in the note book from top to a

center of a page. These lines represent the line along the chain line and in

between are entered the distance along the traverse.

b) At the bottom of the page write the name of the line being booked.

c) Enter the measurements at points along the line from which tape distance,

tie lines and offsets are taken to object.

d) If the building is located it is plotted so that its corners which are located by

tie lines fit the points already obtained.

Booking format the surveyed measurements in the field note book looks as

follows

Tie – out

41.8

7.4 33.3 6.0

27.5

8.0

21.1

14.2

2.0 14.3

10.2 2.0 9.3 15.4

7.2 3.8 2.5

00

Fig.1.129 The booking sheet for line between the two buildings.

Office work: This is the post field work stage in which data collected and recordings

in the field notebooks are decoded and used to prepare the charts, planes and maps

for presentation to the clients and the target audience.

CHAIN SURVEYING OBSTACLES AND WAYS TO OVERCOME THEM

Agor, (1993) classified the various types of obstacles encountered in the course of

chaining into three: Obstacles which obstruct ranging but not chaining; Obstacles

which obstruct chaining but not ranging; Obstacle which obstruct both ranging and

chaining.

Obstacles that obstruct ranging but not chaining

Here, there is lack of inter-visibility between the ends of a chain line. This occurs in

an undulating terrain.

Obstacles which obstruct chaining but not ranging.

Water bodies like lakes, ponds and rivers are typical examples of obstacles in this

category. It is possible to chain around these obstacles by using the Rectangulation

method which is done through constructing rectangles or Triangulation method

which is done through the construction of similar triangles:

Pond: A survey may encounter an obstacle of a pond during the chain surveying

and in order for the chaining to continue the obstacle should be avoided. If chaining

has reached point A and encountered an obstacle. To get to point B, mark C, D, E

and F with an arrow. Set of perpendiculars CD and EF high enough to clear the

obstacles. Join and measure CD which now equals EF. This allows chaining to

continue from D as described below.

A

B

As long as figure in the figure above CDEF is rectangle with sides CD = EF and CF =

DE, then the total length AB will be obtained by adding the lengths AC, CF = DE,

and F. Therefore, the measured distance or length of AB = AC+ DE+FB

Triangulation method is done through constructing similar triangles

Pond: To continue chaining from B, fix a point E away from the obstacle. Range a

pole at G to align with CE hence CE = EG. In line with BC range another pole F in

line with DE. Hence DE = EF. Measure FG which equals CD hence chaining can

continue from B.

D

EF

Pond

C

A

F

G

B

b)River:

To overcome the obstacle of the river is done by constructing similar triangles as

depicted in the figure below. If the chaining has reached A from initial point (T0),

and unfortunately surveyor meet an obstacle of a stream which cannot be ranged.

For the effective chaining, surveyor must overcome it. Through considering the

illustration of stream as drawn below as an obstacle during the chain surveying,

surveyor can follow the following procedures in order to overcome the obstacle.

1. Establish the direction of the chain line across a river from T0 to T1 though

point A and B.

2. At point B, establish any perpendicular convenient chain line towards another

point E at one end of the river bank.

3. Erect a perpendicular line AE through C as mid-point at any convenient

distance

4. At point D, erect the perpendicular line DF and for that case range pole F is in

straight line with range pole B and C, that makes line BCF to be a straight

line. In this case the triangles BAC and FEC are congruent, and line AB is

equal to line EF.

C

D

E

T1

B

To F

From the illustration above, the two triangles BAE and DCE created are congruent

which implies that length CD = length AB which is the required length hence

chaining can now proceed from B to the final terminal (T1).

Therefore, T0T1 = T0A + EF + BT1

Obstacles which obstruct both ranging and chaining

The surveyor cannot easily range and chain in the area with features like tall

buildings, forest and big block of rocks. These obstacles during the chain surveying

obscure both ranging and chaining. And if the surveyor cannot see through the

obstacles, the chain line can be conducted and measured through the following

procedures.

1. Establish the chain line across the house and if the chaining has reached

point A from T0 where an obstacle like a building has been reached as

illustrated below.

2. Establish beyond the house another point B and point T1 exactly aligned

along the chain line.

CA E

3. At pin A and B, erect any convenient equidistant perpendicular lines to clear

an obstacle. If that is the case, line AC will be equal to the line BD.

4. Set off perpendicular line CD that will be equal to imaginary line AB. AS T0,A,B

and T1 are on chain line and obstacle AB has already cleared with line CD,

then surveyor must continue to measure from B to T1.

2. TRAVERSING SURVEYING

Definition: Traversing surveying is that type of survey in which a number of

connecting survey lines form the frame work and the directions and lengths of the

survey lines are measured with the help of an angle measuring instrument and a

tape respectively. Traversing survey as the type of land or ground survey is

conducted by fixing of a bearing position in the field. The bearing is measured

through measuring the angles of bearing between the line of magnetic North and

the line of the sight to the object. Traversing surveying is also known as prismatic

compass surveying, compass surveying or compass traversing. Compass traverse

involves fixing of a point in the field by measuring the angle of bearing from another

known point.

BA

C D

To T1

A traverse is a series of connected lines whose lengths and directions are measured

in the field. The survey performed to evaluate such field measurements is known as

traversing. The lines on the traverse are known as legs and points as stations.

Traversing can be achieved by using the simple angular measuring instrument such

as a prismatic compass or a sophisticated instrument such as a theodolite. In

prismatic compass survey several kilometers from the observer to the objects can

be plotted. A traverse is developed by measuring the distance and angles between

points that found the boundary of a site

Principle - In Compass survey chain or tape is used for linear measurements and

compass is used for fixing direction. In compass freely suspended magnetic needle

directs to north- south and the bearing of line is obtained by line of sight.

Uses of Traverse Surveying

i. Traverse surveying is used where the conditions make the chain triangulation

method impossible, i.e. a woody area, built up areas or long winding rivers.

ii. It also used where the survey is of a large area and details are not required.

Types of Traverse

i. The Closed Traverse

A closed traverse is a series of distances and angles that form a closed figure. The

closed traverse is the one which proceed from known point to another and back to

the known point. This type is used for surveying closed features such as forest, lake,

building blocks or other areas across which no ties, or check lines, can be run. Such

a traverse can be easily checked as the survey starts and finishes at a fixed point or

points.

Figure 1.132 : Closed traverse

ii. An Open Traverse

An open traverse is a sequence of angles and distances that define a line or route,

but does not form a closed figure. The open traverse is one that proceeds from one

point to another but which does not close back to the known point. This type of

traverse is used to survey rivers, roads or railway routes.

Instruments used in prismatic compass survey

The various instruments used in the compass survey are: Prismatic compass, Tape,

Ranging rods, Tripod, Arrows. Although tape, ranging poles or rods are already

discussed in this chapter, here we are going to discuss little bite on the prismatic

and tripod stand as prismatic compass survey’s instruments.

Prismatic compass

Prismatic Compass comprises of a magnetic needle attached to the circular ring

made up of aluminium. The needle is on the pivot and will orient itself in the

Figure. 1.133 : Open traverse

F

E

D

C

B

A

magnetic meridian Therefore the north and south ends of the ring will be in this

direction. The line of sight is defined by the objective vane and the eye slit, both

attached to the compass box. The object vane consist of a vertical hair attached to

a suitable frame while the eye slit consist of a vertical slit cut in to the upper

assembly of the prism unit, both being hinged to the box.

When an object is sighted, the sign vanes will rotate with respect to the N-S end of

ring through an angle which the line makes with the magnetic meridian. A triangular

prism is fitted below the eye slit, having suitable arrangement for focusing to suit

different eye sight. The readings increase in clockwise direction from 0o at South

end 90o at West end 180o at North end and 270o at East end. The object vane frame

can be folded on the glass lid which covers the top at box. The object vane presses

against a bend lever which lifts the needle of the pivot and holds it against the glass

lid. When bright objects are sighted dark glass may be interposed in to the line of

sight.

Figure

1.134:

Prismatic Compass

Tripod stand

Figure 1.135: Samples of tripod stands

Adjustments in prismatic compass survey

The following are the adjustments usually necessary in the prismatic compass:

Centering, Leveling & focusing the prism

Centering: The center of the compass is placed vertically over the station point by

dropping a small piece of stone below the center of the compass, it falls on the top

of the peg marking that station.

Levelling: By means of ball and socket arrangement the Compass is then leveled

the graduated ring swings quite freely. It may be tested by rolling around pencil on

the compass box.

Focusing the prism: The prism attachment is slid up or down focusing till the

readings are seen to be sharp and clear.

Observing Bearing and azimuth

Definition

A bearing is defined as the acute horizontal angle between a reference meridian

and the line. The angle is measured from either the north or south towards the east

or west, to give a reading smaller than 900. The bearing of a line is measured from

the north or from the south (whichever is closer), in a clockwise or counterclockwise

direction (whichever applies). It requires two letters and numerical value e.g. N450E.

It may be true/magnetic/assumed, forward/back. The position of an area can be

shown by using bearing. There are two systems commonly used to express the

bearing.

Whole circle bearing: In this system the bearing of a line is measured with the

magnetic north in clockwise direction. The value of bearing thus varies from 0o to

360o. In this system the bearing is stated without indicating the direction of the

object or observer.

Quadrantal system: In this system the bearing of a line is measured eastward or

westward from north or south whichever is near. The directions can be either clock

wise or anti clockwise depending upon the position of the line. Bearing directions

are shown by using the compass bearing which shows main compass directions or

cardinal points. The bearing the shown by direction such as east, west, north, south,

north east, south west and so forth. Thus, the starting point in stating the direction

of a particular area is 0000N towards 3600N.

There are three types of cardinal points which are four cardinal points, eight

cardinal points, and sixteen cardinal points.

FOUR CARDINAL POINTS

0000N

2700W 900E

1800S

If all 4 cardinals=3600

1cardinal=X

X=3600/4=900

Therefore, in 4cardinal points each cardinal point contains 900

EIGHT CARDINAL POINTS

0000N

N3150W N450E

2700W 900E

2250S S1350E

1800S

If 8cardinal points=3600

1 cardinal point=X

X= 360 0 =450

8 Therefore, in 8 cardinal points each cardinal contains 450

SIXTEEN CARDINAL POINTS

0000N

NNW NNE

N 3150W N450E

NWN NEN

2700W 900E

SWS SES

S 2250 W S1350E

SSW SSE

1800S

If 16cardinals points= 3600

1 cardinal point=X

3600×1 X= =22.50 16 Therefore, in 16 cardinal points each cardinal contains 22.50.

Types of BearingThere are two types of bearings which are forward bearing and back ward bearing.

Forward bearing is the type of bearing in which the reading is taken by an observer

to the object along a line of sighting. The bearing of the line in the direction of

progress of the survey is called Fore Bearing (FB).

Back bearing is the type of bearing in which the reading is taken by the observer

from an object. The bearing in the opposite direction is called Back Bearing

(BB).Back bearing is used for checking the accuracy of forward bearing reading

taken from the observer to the object along the sight line. It is checked by noting

the difference in degree between the Back Bearing and Forward Bearing. Always

the difference between the Back Bearing and Forward Bearing is exactly1800 or 0000

and if it is less or greater than these readings has an error which need to be

corrected.

Station A

Station B

The compass always points toward magnetic north, so when making a compass

traverse the angles of the line of a traverse (leg) is related to the north-south line of

the compass needle. For example, if you conduct a compass traversing from station

A to station B, the Angle between north and AB is known as a forward bearing of AB

and the angle between north and AB at station B is known as the back bearing of

AB.

If there is a local attraction the compass needle is diverted from the north-south line

and the compass reading will be inaccurate. Where there is a local attraction the

back bearing and the forward bearing difference will not be 1800. As the back

bearing and forward bearing differ by exactly 1800. The presence of metals,

metallic ores or electric currents causes the local attraction, therefore the stations

should be chosen so that they are beyond the influence of local attraction.

Principles

If forward bearing>1800, Back Bearing (BB) = Forward Bearing (FB) ─ 1800and

If forward bearing<1800, Back Bearing (BB) =Forward Bearing (FB) +1800

Consider the figure below that show forward and back bearings of lines AB and BC.

B

C

A

Forward bearing of BC

Back b

eari

ng

of

BC

2800

Back bearing of AB

60

0 F

orw

ard

beari

ng

of

AB

1000

2400

Example1. Find back bearing under the following forward bearing:-

i. S1550SE

ii. 3600N

iii. 1850S

SOLUTION

Given Forward Bearing=1550 since FB<1800, then

Back Bearing (BB) =Forward Bearing+1800

=1550+1800

=3350

The back bearing for forward bearing S1550SE is N3350W

Given Forward Bearing =3600 since FB>1800, then

Back Bearing (BB) =Forward Bearing ─1800

=3600 ─1800

=1800

The back bearing for forward bearing 3600 is 1800S.

Given forward bearing=1850 since FB >1800, then

Back Bearing (BB) =Forward bearing-1800

= 1850 ─1800

=0050

The back bearing for the forward bearing 1850 is 0050N.

ERRORS IN PRISMATIC COMPASS SURVEY

The errors may be classified as 1.Instrumental errors 2.Personal errors 3. Errors due

to natural causes.

Instrumental errors - They are those which rise due to the faulty adjustments of the

instruments. They may be due to the following reasons:

a) The needle not being perfectly straight.

b) Pivot being bent

c) Sluggish needle

d) Blunt pivot point

e) Improper balancing weight

f) Plane of sight not being vertical

g) Line of sight not passing through the center of graduated ring

Personal Errors – They are those which rise due to the human imperfection. They

may be due to the following reasons:

a) Inaccurate leveling of the compass box.

b) Inaccurate centering. Inaccurate bisection of signals.

c) Carelessness in reading and recording.

Natural errors - They are those which rise due to the natural factor of an area. They

may be due to following reasons:

a) Variation in declination

b) Local attraction due to proximity of local attraction forces.

c) Magnetic changes in the atmosphere due to clouds and storms.

d) Irregular variations due to magnetic storms etc.

e) Intersection method to plot the area using a compass

Compass Traverse Procedure and Plotting

The following will be procedures during the compass traverse survey when

conducted in certain area.

i. Held a prismatic compass over a station and take the bearing reading of

the forward station.

ii. Held the compass over the same station and take the bearing over the

back station and record it.

iii. The distance to the forward station is measured and recorded and the

process of sighting the bearing is repeated at each following station until

all the stations are complete.

iv. The field measurements are reduced and the traverse is plotted with to

scale.

LOCAL ATRACTION EFFECT AND ITS CORRECTION IN PRISMATIC OR TRAVERSING

SURVEY.

Definition of local attraction

Consider the example of the field ABCD given below then correct the effect

of local attraction if exist.

Actual bearings recorded.

At AB: Forward bearing = 600, BA: Back bearing =2400, then the diff. =1800

BC: Forward bearing = 1200, CB: Back bearing =3000, then the diff. =1800

CD: Forward bearing = 2100, DC: Back bearing =320, then the diff. =1780

DA: Forward bearing = 3170, AD: Back bearing =1350, then the diff.1820.

This indicate at D there is a local attraction effect since the forward and back

bearing at D do not vary by 1800.This attraction causes the bearing at D to be 1820

instead of 1800. To correct the effect of local attraction the 2 degrees is subtracted

from each of the bearing at D. After applying the correction of -2 degrees the

bearing at D will be corrected.

Table below shows the corrected bearings as it affects point D:

Line Bearings Different exist between

bearings

Discrepancy

(error)

Corrected

bearings

AB 600 000 600

BA 2400 000 2400

BC 1200 000 1200

CB 3000 000 3000

CD 2100 000 2100

DC 320 -20 300

AD 3170 -20 3150

DA 1350 000 1350

3. PLANE TABLE SURVEYING

Plane table is a graphical method of surveying in which the field works and the

plotting is done simultaneously. It is particularly adopting in small mapping. Plane

table surveying is used for locating the field computation of area of field. The plane

table consists of a drawing board with arrangement for fixing on a tripod stand. The

plan is drawn by the surveyor in the field, while the area to be surveyed is before

his eyes. Thus, there is no possibility of omitting the necessary measurements.

There are various types of plane tables, depending upon the arrangement of fixing

the boards to the tripod, leveling off the table and rotating arrangement in a

horizontal plane. Figure 1.---. shows a sample plane tables.

1800

1800

1780

1820

Figure1.--. Samples of plane tables

Principle of plane table

ADVANTAGES AND DISADVANTAGES OF PLANE TABLE SURVEY

Advantages of Plane Table Survey

1) It is suitable for location of details as well as contouring for large scale maps

directly in the field.

2) As surveying and plotting are done simultaneously in the field, chances of

getting omission of any detail get less.

3) The plotting details can immediately get compared with the actual objects

present in the field. Thus errors as well as accuracy of the plot can be

ascertained as the work progresses in the field.

4) Contours and specific features can be represented and checked conveniently

as the whole area is in view at the time of plotting.

5) Only relevant details are located because the map is drawn as the survey

progresses. Irrelevant details get omitted in the field itself.

6) The plane table survey is generally more rapid and less costly than most

other types of survey.

7) As the instruments used are simple, not much skill for operation of

instruments is required. This method of survey requires no field book

Disadvantages of Plane Table Survey

1) The plane table survey is not possible in unfavorable climates such as

rain, fog etc.

2) This method of survey is not very accurate and thus unsuitable for large

scale or precise work.

3) As no field book is maintained, plotting at different scale require full

exercise.

4) The method requires large amount of time to be spent in the field.

5) Quality of the final map depends largely on the drafting capability of the

surveyor.

6) This method is effective in relatively open country where stations can be

sighted easily.

INSTRUMENTS OF PLANE TABLE

A plane table mounted on a tripod stand and a number of accessories are used

during plane table survey. The accessories consist of alidade, spirit level, trough

compass, plumbing fork, plumb bob, drawing sheet.

Alidade

An alidade is a device in which the vertical plane of the line of sight is maintained

parallel to a straight-edge ruler on which the sighting arrangement is kept. It is used

to draw a line parallel to the line of sight and thus provides the direction of the

object to be plotted. Depending on the type of sighting arrangement, alidades are

classified as Plain Alidade, Telescopic Alidade and digital alidade.

Plain Alidade: It consists of a straight-edge ruler, made of a metal or wood, with one

of the edges is beveled and graduated known as fiducial edge. It consists of two

vanes which are perpendicular to its ends, fitted with hinges at their bases, known

as sight vanes. These are kept folded down on the ruler when not in use. One of the

sight vanes is provided with a narrow slit having three holes. This is used as eye

vane. The other, used as object vane, is open and carries a hair or thin wire at its

center. Thus, the line passing through the slit of the eye vane joining the thin wire

of the object vane and passing beyond is known as the line of sight of a plane

alidade. A string is fitted at the top of the sight vanes and is used for inclined sight.

In some alidade, a compass needle as well as a spirit level gets fitted in a box

engraved at its base. However, the plain alidade is not very accurate. (Figure 33.2)

show a plain alidade.

Figure 33.2 Plain Alidade

Digital Alidade: It consists of an EDM, with a built-in telescope for sighting, an

automatic angle sensor for registering vertical angle and a microcomputer for

yielding horizontal distance and difference in elevation. It also consists of a liquid

crystal display which is used to display and thus read and retrieve the observed and

calculated parameters. Digital alidade is particularly useful for accurate plotting of

detail and for the long line of sigh. It consists of a telescope as an arrangement for

sighting (similar to that present in the upper part of a theodolite). The telescope is

fitted with a stadia diaphragm and can be used as tachometer also for computations

of horizontal distance and vertical elevations. The line of sight of the telescope is

aligned along the fiducial edge. In this instrument, the object is sighted through the

telescope and the distance is scaled off in that direction along the fiducial edge.

Figure 33.3 shows a telescopic alidade

Figure 33.3 Telescopic Alidade

The telescopic alidade is designed for greater precision and longer range of sights.

It can be used with advantages for contouring and plotting of details during

topographic surveying.

Plumbing ForkA plumbing fork is a U-shaped piece of metal or wooded frame (Figure 33.4). The end of one of its arm is pointed and the other arm is having an arrangement for hanging a plumb bob. The frame is constructed in such a way that the tip of the pointed arm and the plumb line lie in the same vertical line. At the time of use, the pointed arm is placed on the table and the other arm, with a plumb bob attached, is kept below the table. Plumbing fork with a plumb bob is used in large scale surveying for centering of plane table and for Transferring of ground point.

Figure 33.4 Plumbing ForkSpirit Level: It consists of flat based tube with a small bubble either circular or tubular in shape. It is used to check the level of plane table by placing it on the board in two positions at right angles to each other. When the bubble tube remains in the center at any point on the table is considered to be properly leveled. Figure 1.---. shows a spirit level.

Figure 1.---.Spirit LevelTrough Compass: A trough compass consists of a long, narrow rectangular box,

covered with glass. Inside the box, at its center, there is a magnetic needle resting

on the pivot. At the extremities of the trough compass, there are graduated scales

with zero at the center and marking up to 5° on either side of the zero line. Figure

1.126 shows a Trough compass

Figure 1.126: Trough Compass

The trough compass is used for marking the magnetic north line on the drawing

sheet of the plane table. It determines the North and South line. In this case, the

magnetic needle point to 0° - 0° of the graduated scale and a line drawn parallel to

the edge of the trough compass is along the magnetic meridian. A trough compass

is also used to orient the plane table with respect to the magnetic meridian.

Drawing board mounted on tripod

A sheet of drawing paper, called plane table sheet is fastened to the board. Board is

made up of well-seasoned wood such as teak of size 40x30 to 75x60cm with plane

and smooth top. It is mounted on a tripod in manner that it can be leveled. Leveling

up of the table is done by shifting the legs of tripod. Some tripod provided with

leveling screw or by ball and socket head for accurate leveling.

TEMPORARY ADJUSTMENTS OF PLANE TABLE

It is necessary to check whether the accessories satisfies some basic conditions and

if required, necessary adjustments are to be done before starting any plane table

surveying work. The operations involved in this are known as temporary adjustment

of plane table. Following three distinct operations at each survey station are carried

out for the temporary adjustments of a plane table. These operations include

Centering, Leveling and Orientation. The conditions needed to be tested and

subsequent adjustments are as follows:

1. The surface of the board should be a perfectly plane.

Test: It is tested by placing a straight edge on the top surface of the plane table in

different directions. If there is no gap between the base of the straight edge and the

surface of the plane table then the surface is perfectly plane. Otherwise, the surface

is not perfectly plane.

Adjustment: If the gaps are minute, those are removed by rubbing with sand paper

and for more gaps, the table should be replaced.

2. The fiducial edge of the alidade should be straight.

Test: It is tested by drawing a fine line on the paper along the fiducial edge of the

alidade. Then, by reversing the alidade, end for end, and placing against the line

drawn, a line is to be drawn again along the fiducial edge. If the two lines coincide,

the edge is straight. Otherwise, the edge is not straight.

Adjustment: The fiducial edge of the alidade is to be made straight by filing and

then test is repeated till satisfactory outcome.

3. In fully opened condition, the sight vanes of the alidade should be perpendicular

to its base.

Test: Hang a plumb bob at a distance of about 5 to 10 m from the plane table.

Bisect the string of the plumb bob through the alidade placed on properly leveled

plane table. If the sighting slit, the object vane hair and the plumb bob string lie the

same vertical line, the vanes of the alidade are perpendicular to the base of the

alidade. Otherwise, it requires adjustment.

Adjustment: is being carried out by inserting packing under the base of the sight

vanes or by filing the base, as required. The test and adjustment get repeated till

satisfactory outcome is achieved.

The telescopic alidade if used should be in perfect adjustment. The testing and

adjustment of the telescopic alidade are to be carried effectively.

Centering: It is the process of keeping the table over the station that the point on

the paper representing the station being occupied is vertically over the point on the

ground. It is done by forked plumb bob. The legs of tripod are well spread out to get

the convenient height for working on the board. Then, the operation of centering is

carried out by means of plumbing fork or U-frame and plumb bob. This process

ascertains the fact that the point on paper represents the station point on ground.

The pointed end of the plumbing fork is kept on point on paper and at the other

end, a plumb bob is fixed. The table or board is shifted bodily till the plumb bob

hangs exactly over the peg of the station.

Leveling: The process of leveling is carried out with the help of spirit level and it

consists of making the table level either by ordinary tilting the board or by ball and

socket arrangement or by adjusting the legs of tripod.

Orientation or positioning of Plane Table: The objective of this operation is to

maintain the orientation of the table constant at all the stations in any particular

plane table surveying i.e., the four edges of the plane table will always be in the

same direction at all the stations. Thus, all lines plotted on the plane table sheet will

maintain parallism to their corresponding lines on the ground. During orientation,

the leveling of the plane table generally gets disturbed so it is usually carried out

with leveling simultaneously iteratively. The orientation of plane table can be

carried out by using a trough compass; back sighting; resection.

Orientation by using Trough Compass: In this method, the edge of the trough

compass is placed along the magnetic meridian (drawn at the starting station) and

the plane table is rotated till the needle points to zero-zero of the scale. Once it is

achieved, the table is said to be oriented and thus clamped. This method of

orientation is not very accurate and also may get affected by local attraction and is

generally used for small-scale survey.

Orientation by Back sighting: In this method, the fiducial edge of alidade is laid

along a ray drawn from previous station to the present station and the plane table is

then rotated till the line of sight of alidade bisects exactly the ranging rod placed at

previous station. The plane table is then clamped and said to be oriented. In this

method, the level of the plane table has to be maintained identical in both the

stations.

ERRORS AND PRECAUTIONS TO BE TAKEN IN PLANE TABLE SURVEY.

METHODS OF PLANE TABLE SURVEY:

Following are the four methods by which an object might be located on paper by

plane table including Radiation; Intersection; Traversing and Resection.

RADIATION

This is the simplest method and it is useful only when the whole traverse can be

commanded from a single station. Here, the plane table is set up at one station

which allows the other station to be accessed. The points to be plotted are then

located by radiating rays from the plane table station to the points. After reducing

the individual ground distances on the appropriate scale, the survey is then plotted.

This method is suitable for small area surveys. It is rarely used to survey a complete

project but is used in combination with other methods for filing in details within a

chain length. The procedure is as follows:

1. Select a point P so that all the corners of the traverse ABCD are seen.

2. Carry out the usual temporary adjustments of centering and leveling. Mark

the north line on paper.

3. Put the alidade on point P and dram a line of sight for station A.

4. Measure the distance PA on ground and put this length to a suitable scale on

paper which will give point a.

5. Similarly, obtain points b, c and d on paper by drawing lines of sight for

stations B, C and D and measuring the distances PB, PC and PD on ground

respectively.

6. Join points a, b, c and d on paper, as shown in figure.

7. For checking the accuracy of work, measure the distances AB, BC, CD and DA

on ground and compare them with the lengths ab, bc, cd and da respectively

on paper.

ad

b

c

A

B

C

INTERSECTION METHOD

This method is useful where it is not possible to measure the distances on ground as

in case of a mountainous country. Hence, this method is employed for locating

inaccessible points, the broken boundaries, rivers, fixing survey stations, etc. In this

method, two instrument stations are used with the distance between them called

D

based line serving as the base to measure and plot the other locations: The

procedure is as follows:

i. Select two stations P and Q so that the points to be located on paper are

easily seen from them.

ii. Plot the line pq, which is known as the base line, on paper. This can be done

in one of the two ways:

a) The table can be centered and leveled at station P and then after

orienting at station Q, the distance PQ can be accurately measured

and put up to some scale on the paper.

b) The line pq can be drawn to some scale on the paper and then the

board can be adjusted from station P by back sighting at station Q.

iii. From station P, draw rays for stations A, B, etc.

iv. Shift the table to station Q and after proper orientation, take rays of stations

A, B etc.,

v. The intersection of rays from stations P and Q will give points r, s etc. on

paper, as shown in figure.

vi. For checking the accuracy of work, measure the distance AB on ground and

compare it with its corresponding length rs on paper.

Dc

qp

e

p q

c

A B

C

Q P

Fig. Plane Tabling using Intersection Method

TRAVERSING METHOD

Plane table

r s

This method resembles the compass traversing in which the plane table is set up at

each successive and the back sight taken station until all the stations are

covered.

PROCEDURE:

1. Set up the plane table over station A

2. With the Alidade at a sight B, measure AB and using appropriate scale draw

the distance ab to correspond with ground distance AB.

3. Transfer the table to B and position b to B. from b sight, measures scale AB

and insert as ab on the paper.

4. Relocate the station to C and sight D from there. Continue the procedure until

all the stations are covered as shown in the diagram

C

D

E

a

c

bb

a

Fig. : Plane Tabling using Traversing

Method

Resection Method

The resection method is used for locating the station

points by means of drawing rays from the stations whose

locations have already been plotted on the sheet. This

carried out using various procedures:

1. In the simplest method, select a base line AB on the

ground, measure and plot ab on paper. Set up the

plane table at B in a position where b corresponds to B.

2. From b sight C and draw a ray to represent the approximate location of C

locate this position as C.

3. Set up the instrument at C and draw a ray to A, the tone position of C is the

point of intersection made between the ray and that made from b

A B

c’

a b

c’

c

a b

Figure. Plane Tabling using Resection Method

C

A

B

Exercise

1) What do you understand by plane table survey? What are the

advantages and dis-advantages of Plane Tabling? List the different

accessories used in plane tabling along with their uses.

2) Describe the steps involved in setting up of a Plane Table.

3) Explain the different operation involved in temporary adjustment of

plane table surveying.

4. LEVELLING IN SURVEY

The act of establishing the elevation of points on or below the surface of the earth is

called leveling. It is the methods of surveying that deal with determining height and

representing them. Levelling enables surveyors to survey in a vertical scale.

Levelling is therefore surveying in a vertical plane. The elevation of a point on the

surface of the earth is actually the difference in attitude between the point and

some datum or base level. Hence, leveling makes use of a base level to determine

the height of any point. The sea level is the base level of topographic maps. The aim

of levelling is to determine the relative heights of different objects on the surface of

the Earth and to determine the undulation of the ground surface.

Usually the vertical direction is parallel to the direction of gravity; at any point, it is

the direction of a freely suspended plumb-bob cord. The vertical distance of a point

above or below a given reference surface is called the elevation of the point. The

most commonly used reference surface for vertical distance is mean sea level. The

vertical distances are measured by the surveyor in order to determine the elevation

of points, in a process called running levels or leveling. The determination and

control of elevations constitute a fundamental operation in surveying and

engineering projects.

Leveling provides data for determining the shape of the ground and drawing

topographic maps and the elevation of new facilities such as roads, structural

foundations, and pipelines.

Uses of levelling

Levelling is done for the following purposes:

i. To prepare a contour map for fixing sites for reservoirs, dams, barrages

etc., and to fix the alignment of roads, railways, irrigation canals, and so

on.

ii. To determine the attitudes of different important points on a hill or to

know the reduced levels of different points on or below the surface of the

Earth.

iii. To prepare the longitudinal and cross section of a project (roads, railways,

irrigation canals, etc.) in order to determine the volume of Earth work.

iv. To prepare a layout map for water supply, sanitary or drainage schemes.

TECHNICAL TERMS USED IN LEVELLING

Level Surface: A level surface is a surface which is everywhere perpendicular to the

direction of the force of gravity. An example is the surface of a completely still lake.

For ordinary levelling, level surfaces at different elevations can be considered to be

parallel.

Level Datum: A level datum is an arbitrary level surface to which elevations are

referred. The most common surveying datum is mean sea-level (MSL), but as

hydrological work is usually just concerned with levels in a local area, we often use:

An assumed datum, which is established by giving a benchmark an assumed value

(e.g. 100.000 m) to which all levels in the local area will be reduced. It is not good

practice to assume a level which is close to the actual MSL value, as it creates

potential for confusion.

Level books: All levelling shall be booked in either level books or levelling sheets

which shall be retained as permanent records. Level books shall be numbered so

that they can be referenced on station history and inspection forms. They should be

stored in fire-proof storage as for original record. They should also include an index.

Levelling sheets shall be filed in time-sequential order in site files, and also need to

be in fire-proof storage as for level books.

Back sight: This is the first reading on the staff placed on a benchmark at the

commencement of levelling operation. It is first reading taken to a point whose

height is either known or can be calculated.

Foresight: Foresight is the reading taken at a point where the elevation is not yet

known. It is the reading taken at a point whose height is required in order for the

levelling operation to continue.

Intermediate foresight (IS): is a rod reading taken on any point where an elevation

is required. All staff reading between B.S. and F.S. are Intermediate sight. It is used

in many engineering levelling projects such as profiles or cross-sections or in open

pit mining surveys where specific ground elevations would be needed to calculate

volumes of material.

Orders of levelling: refer to the quality of the levelling, usually being defined by the

expected maximum closing error. These are given in Table below

Order Purpose Maximum close

(m)

Precision

order

Deformation surveys 0.001 x km

First order Major levelling control 0.003 x km

Second

order

Minor levelling control 0.007 x km

Third order Levelling for 0.012 x km

construction

Table 1. Levelling closes

Reduced Level: This is also called reduced height and is the calculated elevation of

a place above or below sea level. A reduced level is the vertical distance between a

survey point and the adopted level datum.

Bench mark (BM): A bench mark (BM) is the term given to a definite, permanent

accessible point of known height above a datum to which the height of other points

can be referred. It is usually a stainless steel pin embedded in a substantial

concrete block cast into the ground. At hydrological stations rock bolts driven into

bedrock or concrete structures can be used, but structures should be used warily as

they themselves are subject to settlement. The locations of benchmarks shall be

marked with BM marker posts and/or paint, and recorded on the Station.

The roughly 600,000 vertical control points in the U.S. National Spatial Reference System (NSRS) are referenced to the North American Vertical Datum of 1988 (NAVD 88).

The benchmark is a fire hydrant with the word "OPEN" on top. The elevation is 26.295 feet above sea level at the top of the letter "O". This is an Official benchmark elevations in San Francisco that is available from the Bureau of Street Use andMapping. (Located at 875 Stevenson Street, Room 460 /// San Francisco, CA. 94103 ///415.554.5810).

Source: Degree Engeeringgaurav.tandonlevelling&countering.pdf

Figure: Sample of bench marks

Temporary bench mark (TBM): A temporary bench mark is a semi-permanent

point of known elevation established from a known BM. It is used for

convenience the site to transfer elevations for different stages of a

construction project.

Arbitrary bench marks: These are reference points whose R.L.s are arbitrarily

assumed. They are used in small works such bench mark may be assumed

as 100 or 50 m

Set-up: A set-up refers the position of a level or other instrument at the time in

which a number of observations are made without mooring the instrument. The first

observation is made to the known point and is termed a back sight (The site taken

after the level has been taken); the last observation is to the final point or the next

to be measured on the run and is termed as fore sight (The last sight taken), and all

other points are intermediates.

Run: A run is the levelling between two or more points measured in one direction

only. The outward run is from known to unknown points and the return run is the

check levelling in the opposite direction.

Close: A close is the difference between the starting level of the initial point for the

outward run and that determined at the end of the return run. If the levels have

been reduced correctly this value should be the same as the difference between the

sum of the rises and falls and also the difference between the sum of the back

sights and foresights.

Change points: Change points are points of measurement which are used to carry

the measurements forward in a run. Each one will be read first as a foresight, the

instrument position is changed, and then it will be read as a back sight.

Turning point (TP)

Line of collimation:-It is a line joining the intersection of cross hairs of diaphragm to

the optical center of object glass and its continuation. It is also known as line of

sight.

Height of Collimation: Height of Collimation is the elevation of the optical axis of the

telescope at the time of the setup.

Line of collimation: The line of collimation is the imaginary line at the elevation.

INSTRUMENTS FOR LEVELLING

The following instruments are essentially required for levelling

Levels: The instrument used to furnish horizontal line of sight for observing staff

readings and determining R.L.s. The level is used to accurately determine the

difference in elevation between two points on the earth’s surface. By itself, it does

not read or register heights but gives a horizontal line of sight so that in looking

along it, places lying along the same height can be seen, varieties of levels exist

and their difference lines in the level of complexity. Level include tube water level,

Dumpy level, Abney level, Tilting level, Wye level, Automatic level

Dumpy level

More modern types of dumpy levels are still used by builders and contractors, but

have been largely superseded for survey work. Before the introduction of 'digital

levels' with electro-optical staff readings in the 1990s, a more common type of level

was the 'automatic level' , which is constructed in a manner similar to the dumpy

level, in that the telescope is rigidly fixed to the vertical axis of rotation. However,

the difference between the two is that automatic levels feature an optical-

mechanical 'compensator' suspended under gravity, which automatically adjusts

the line of collimation without the need of a level tube.

This dumpy level by Baker is one of the two major types of levels available in the

instrument collection. It is the simplest form of levelling instrument consisting of

two main parts: the tribrach and the telescope. The tribrach has four foot screws

which are used to give the telescope the required horizontal line-of-sight. The

instrument has a vertical axis, around which the telescope can be rotated to sight to

a staff. No other adjustment is possible between the telescope and the tribrach.

The level is fitted with a long sensitive bubble tube attached to the top of the

telescope which enables the line-of-sight (line of collimation), as defined by the

cross hairs, to form a horizontal line which is perpendicular to the direction of

gravity at that point. The levelling of this tubular bubble is carried out by

manipulating the four foot screws.

There is also a smaller tubular bubble, which is perpendicular to the longer bubble

and hence the line-of-sight of the telescope. This bubble provides the instrument

with an additional adjustment in the direction perpendicular to the telescope's line-

of-sight. Levelling the cross bubble reduces the cross-axis tilt.

In a dumpy level, there is only one axis of rotation - the vertical axis. The initial

levelling of the dumpy level must be done very carefully. Any adjustment of the foot

screws between sightings to the staff alters the height of the line-of-sight.

Abney level -

The Abney Level is an

engineering

instrument which can be used to determine height. It is a surveying instrument

consisting of a spirit level and a sighting tube; used to measure the angle of

inclination of a line from the observer to the target. It is moderately expensive and

of medium size and weight.

Figure1. : Dumpy level by Baker.

Figure. Abney Level

Tilting level: It is also known as I.O.P. level (Indian office Pattern). In this level the

telescope tilts about its horizontal axis hence it is called tilting level

Wye level

The essential difference between wye level and other levels is that in wye level the

telescope is carried by two vertical wye supports. The telescope can be rotated,

moved or even raised in wyes.

Automatic level

It is also known as self-aligning level. It is a recent development. The fundamental

difference between auto level and other levels is that the levelling is not manually

but it is levelled automatically. It is achieved by inclination compensating device.

Water level

A water level is a device used for matching elevations of locations that are too far

apart for a spirit level to span. The water level is made up of 2 glass tubes half filled

with colored water fitted ant a tripod when the two water levels are in line and one

looks along a horizontal line of sight passing through the water surfaces, anything

are sees along this line are of the same level with one’s eye and the water surface.

The surveyor’s level consists of a bubble tube with a telescope attached. The

simplest water level is a section of clear tubing, partially filled with water. Water is

easily procured for use, and easily discarded after use. The ends are held vertical,

and the rest of the tubing lies on the ground or floor. The water level at each end of

the tube will be at the same elevation, whether the two ends are adjacent or far

apart. Water levels have been used for many years. The water level is lower-tech

than the laser level, but it can be more accurate over long distances. To avoid error,

all of the water should be at the same temperature. Other sources of error include

difficulty reading due to meniscus.

If the water level is used often, dye can be added to the water to make it easier to

see. If the water level is used outdoors in winter, antifreeze can be added to the

water

TEMPORARY

ADJUSTMENTS OF A LEVEL

These adjustments are performed at every setup of instrument

Figure. Tube Water level

Setting up the level:-This includes

A) Fixing the instrument on tripod

B) Levelling the instrument approximately by Tripod

Levelling:-Levelling is done with the help of foot screws. The purpose of

levelling is to make vertical axis truly vertical. It is done with the help of foot

screws

A) Place the telescope parallel to a pair of foot screw then hold the foot screws

between thumb and first finger and turn them either inward or outward until the

longitudinal bubble comes in the centre.

B)Turn the telescope through 900so that it lies parallel to third foot screw, turn the

screw until the bubble comes in the centre.

Focusing the eye piece:-To focus the eye piece, hold a white paper in front of

object glass, and move the eye piece in or out till the cross hair are distinctly

seen.

Focusing of object glass:-Direct the telescope to the levelling staff and on

looking through the telescope, turn the focusing screw till the image appears

clear and sharp.

Leveling Staff: A level staff, also called levelling rod, is a graduated wooden or

aluminum rod, the use of which permits the determination of differences in

elevation. Levelling rods can be one piece, but many are sectional and can be

shortened for storage and transport or lengthened for use. Aluminum rods may

adjust length by telescoping sections inside each other, while wooden rod sections

are attached to each other with sliding connections or slip joints.

There are many types of rods, with names that identify the form of the graduations

and other characteristics. Markings can be in imperial or metric units. Some rods

are graduated on only one side while others are marked on both sides. If marked on

both sides, the markings can be identical or, in some cases, can have imperial units

on one side and metric on the other

TheodoliteAn optical instrument consisting of a small mounted telescope rotatable in

horizontal and vertical planes, used to measure angles in surveying, meteorology,

and navigation. In meteorology, it is used to track the motion of a weather balloon

by measuring its elevation and azimuth angle. The earliest theodolite consisted of a

small mounted telescope that rotated horizontally and vertically; modern versions

are sophisticated computerized devices, capable of tracking weather balloons,

airplanes, and other moving objects, at distances of up to 20,000 m (65,600 ft).

Two sides of a modern surveyor's levelling rod.Metric graduations on the left, imperial on the right.

Level staffs or rods

Front view of theodolite Side view of theodolite

A Surveyor using Theodolite Theodolite set up

Levelling procedures

(a) Setting up

o Back sight and foresight distances should be approximately equal to

avoid any errors due to collimation, refraction or earth curvature.

o Distances must not be as great as surveyor cannot be able to read

the graduations accurately.

o The points to be observed must be below the level of the

instrument, but not lower than the height of the staff.

(b) Elimination of parallax

Parallax is the apparent movement of the image produced by movement of the

observer's eye at the eyepiece. It is eliminated by focusing the telescope on

infinity and then adjusting the eyepiece until the cross-hairs appear in sharp

focus. The setting will remain constant for a particular observer's eye.

(c) Booking

o Level books or loose-leaf levelling sheets shall be numbered and

indexed in a register.

o Details of the site, work, date, observer, chainman, booker,

weather, wind, instrument and any other relevant items shall be

entered.

o Enter the first observation (which is on a known point) in the Back

sight column, and sufficient detail in the Remarks column to identify

it. Enter the point's R.L. zero from the site register or plate on the

BM, etc.

o Enter all other points on subsequent lines as intermediates except

the point chosen as the foresight. Identify them in the Remarks

column as above. Enter the foresight on a further line in the

Foresight column.

o Change the instrument to the next setup. Enter the following back

sight on the same line as the previous foresight but in the Back

sight column.

o Repeat the above procedure at each setup on the outward run then

reverse it to work back to the starting point on the return run. The

furthest point out is treated as for all other change points.

CLASSIFICATION OF LEVELLING METHODS

Levelling methods are subdivided into two major categories which are Direct and

Indirect methods. Direct levelling methods describes the method of measuring

vertical distances (difference in elevation) directly with the use of precise or semi-

precise levelling instruments. Direct methods involve simple levelling, differential

levelling, fly levelling, precise levelling, profile levelling and reciprocal levelling. And

indirect methods on the other hand, apply to measuring vertical distances indirectly

or by computation. Unlike direct levelling operations, indirect levelling operations do

not depend on lines of sight or intervisibility of points. Some of the instruments

commonly used for indirect levelling methods are transit and theodolite. Indirect

levelling methods involve trigonometric levelling, stadia levelling and barometric

leveling.

Simple levelling: It is the simplest method used, when it is required to find the

difference in elevation between two points on the ground. It is performed when

the difference of level between two points is determined by setting the levelling

instrument midway between the points. Suppose A and B are the two points

whose difference of level is to be determined. The level is set up at O, exactly

midway between A and B. After proper temporary adjustment, the staff

readings on A and B are taken. The difference of these readings gives the

difference of level between A and B. See the figure below.

A B O

Fig. Simple levelling

Differential or spirit levelling: By far the most common leveling method, and the one

which most surveyors are concerned with, is differential leveling. It may also be

called spirit leveling, because the basic instrument used comprises a telescopic

sight and a sensitive spirit bubble vial. The spirit bubble vial serves to align the

telescopic sight in a horizontal direction, that is, perpendicular to the direction of

gravity. This method finds the difference in the elevation between points if they

are too far apart or the difference in elevation between them is too much. It is

generally used in determining elevation of points to establish a chain or network

of bench marks (BMs) for future use. It requires series of instruments set ups

along the survey route; and for setup, a horizontal line of sight is established,

using a sensitive level. Differential levelling is adopted when (i) the points are

great distance apart (ii) the difference of elevation between the points is large

(iii) there are obstacles between the points. In this method, a horizontal line of

sight is first established with an instrument called a level. The level is securely

mounted on a stand called a tripod, and the line of sight is made horizontal. Then

the surveyor looks through the telescopic sight towards a graduated level rod,

which is held vertically at a specific location or point on the ground. A reading is

observed on the rod where it appears to be intercepted by the horizontal cross hair

of the level; this is the vertical distance from the point on the ground up to the line

of sight of the instrument.

Fig. 1.----Reading the leveling rod through the Level.

Figure 1.----

Leveling rod detail

Generally, if the elevation of point A is already known or assumed, then the rod

reading on a point of known elevation is termed as a back sight reading (plus sight,

because it must be added to the known elevation of point A to determine the

elevation of the line of sight). Consider the figure below. Suppose it is required to

know the difference of level between A and B. The level is set up at points Q1, Q2,

Q3 and Q4 and after temporary adjustment, staff readings are taken at every set

up. The points TP1, TP2and TP3 are known as changing points, then the difference

between A and B is fund out. If the distance is positive A is lower than B and if it is

negative, A is higher than B.

A Q1 Q2 TP2 Q3 TP3 Q4 A TP1 BM =1003.00

Fig. Differential leveling

Fly levelling: Fly levelling is just like differential levelling carried out to check the

accuracy of levelling work. In fly levelling only B.S. and F.S. are taken. It is low

precision method that finds or checks appropriate level, generally used during

reconnaissance survey. It is conducted in order to connect a bench mark to the

starting pints of the alignment of any project. Fly levelling is also performed to

connect the bench mark to any intermediate point of the alignment for checking

the accuracy of the work. In such levelling, only the back sight readings are

taken at every set up of the level and no distances are measured along the

direction of the leveling(fig.-----). The level should be set up just mid-way

between the backsight and the fore sight.

Check levelling: This kind of levelling is carried out to check the accuracy of work. It

is done at the end of the days of the work in the form of fly levelling to connect the

finishing point and starting point. It is operation of running levels for the purpose of

checking the series of levels, which have been previously fixed. At the end of each

day work, a line of level is run, returning to the starting point of that day with a view

to check the work done on that day. Suppose the following information were

obtained from the levelling done in a certain area by the surveyor X and want to

check the accuracy of the work.

Instrument at Reading atA B

A 1.725 1.370 B 1.560 1.235

Then the surveyor must questions himself whether the line of collimation is in

adjustment and or what should be the correct staff reading at A during the second

setup to make the line of collimation truly horizontal and what is the amount of the

collimation error in order to check for the accuracy of the work done.

When the instrument is at A:

Apparent difference of level = 1.725 −1.370 = 0.355m

When the instrument is at B:

Apparent diffrence of the level = 1.560 −1.235 = 0.325m

Since the two apparent differnces are not equal, then the line of collimation is

not in adjustment.

0.355 + 0.325 The true difference level between A and B = = 0.340 (fall from A to B) 2

In second set up:

Correct reading at B = 1.235 (as the level is near B)

Correct staff reading at A= 1. 235 + 0.340 = 1.575m

But the observed staff reading (1.560m) at A is less than the correct reading

(1.575). So, the line of collimation is inclined downwards.

Therefore, the amount of collimation error =1.560 – 1.575 = −0.0015

Reciprocal levelling:

Profile levelling or Longitudinal Section: This method is used for taking levels along

the center line of any alignment like road, railway canal etc. In this operation the

backsight, intermediate sight and foresight are taken at regular intervals, at every

set up of the instrument. The chainages of the points are noted in the level book.

This operation is undertaken in order to determine the undulations of the ground

surface along the alignment.

Fig. Example of profile levelling

Source: Survey Camp Class Notes.pdf (pg. 17)

Booking format of this profile levelling will look as follow:

Fig. Profile field notes

Source: Survey Camp Class Notes.pdf (pg.17)

Cross-sectioning: This operation is carried out perpendicular to alignment at regular

intervals such as 10, 20, 30, 40 m. The idea is to make an estimate of earthwork. It

is the operation of levelling to determine the surface undulation or routine of the

ground transverse to the given line and on either side of it. It is generally performed

in order to know the nature of the ground cross the center line of any alignment.

Precise levelling:-It is used for establishing bench marks for future public use. It is

carried out with high degree of accuracy using advanced instruments.

Trigonometric levelling: This is leveling procedure that involves observing the

vertical (or zenith) angle and slope distance between two points. The difference in

elevation can then be calculated. Within the limits of ordinary practice, triangle BEC

(figure 45) can be assumed to be a right triangle and:

EC = BC x cos (zenith angle)

A major source of error in determining the difference in elevation by this method is

the uncertainty in the curvature and refraction caused by variations in the

atmospheric conditions.

Height of target

Line of sighting

Horizontal line Level surface

Mean sea level

The effects of Earth Curvature and Atmospheric Refraction must be taken into

account when using trigonometric methods to determine elevations. A line of sight

perpendicular to a plumb line lies in a horizontal plane. The earths curved surface

departs from this line by the value c (shown in Figure 45, as the distance E-F). For

most surveys, a practical value for curvature is:

c = 0.667M2

Where M is the sight distance in Miles and c is the earth’s curvature in Feet. Due to

the density of the air, the optical line of sight refracts or bends back towards the

earth, negating about 14% of the effects of curvature. The combined effect of

Curvature and Refraction is:

(c+r) = 0.574M2

There are two acceptable methods to correct for Curvature and Refraction if the

formulas are not applied: (i) Balance the Backsights and Foresights and (ii) Observe

the zenith angles from both ends of the line (reciprocal zeniths).

The effects of Curvature and Refraction increases rapidly with distance as shown in

the table below:

Effects of Curvature and RefractionDistance 200 ft 500 ft 1000 ft 1 mile 2 mile(h) feet 0.001 0.005 0.021 0.574 2.296

When using trigonometric methods to establish accurate elevations, the following

must be taken into consideration:

1. Due to the effects of curvature and refraction, the instrument to target

distance must be kept relatively short. A good rule of thumb is not to exceed

1000 feet.

2. Make sure you understand your equipment’s capabilities. Instruments that

can measure zenith angles and slope distances to a high order of accuracy

will produce good trigonometric elevations.

3. Setup and level your instrument and target carefully. Measure the height of

instrument and height of target accurately.

4. Measure several slope distances and use a representative or mean value.

Make sure that your EDM is correcting for the appropriate atmospheric

conditions.

5. Measure Direct and Reverse zenith angles, and use the adjusted value for

your calculations.

6. For lines longer than 500 feet, correct for curvature and refraction.

Modern Total Station instruments have to build in capabilities to reduce and display

trigonometric elevations.

Refer to figure above, for the following exercise. Given the following:

Elevation of Point A 506.78 ft

Height of Instrument 5.21 ft

Height of Target 5.46 ft

Measured Slope Distance 837.58 ft

Direct Zenith Angle 78°37’42”

Reverse Zenith Angle 281°22’28”

Correcting for curvature and refraction, calculate the elevation of point D.

Barometric levelling: In this method the altitude difference is determined by

means of a barometer. By using special barometers to measure air pressure (which

decrease with increasing elevation), the elevation of points on the earth's surface

can be determined within ±1m. This method is useful for doing a reconnaissance

survey of large areas in rough country and for obtaining preliminary topographic

data.

Hyposometric levelling: The working of Hyposometry for determining the

elevation depends upon the fact that the temperature at which water boils

varies with the atmospheric pressure. The boiling point of water reduces at

higher altitude thus knowing the boiling point of water, the atmospheric

pressure can be calculated and knowing the atmospheric pressure altitude or

elevation can be determined.

LEVELLING MISTAKES AND ERRORSAs with any surveying operation, blunders must be eliminated and errors minimized

while running levels. Misreading the rod is a common blunder; it can be avoided by

always having the rod person check the reading with pencil point or target. Note

keeping mistakes can be particularly troublesome. The computations of HI and

turning point (TP) elevation should be done in the field, as the work progresses. A

simple arithmetic check at the end of the leveling run can be made to avoid

addition or subtraction errors.

a. Random Errors

Unavoidable accidental errors may occur when running levels, for several reasons.

For example: The level rod may not be precise when the reading is taken, heat

waves from the ground make it difficult to read and on windy day, slight vibration of

the cross hair can cause small errors in the reading. The instrument may be slightly

out of level if the spirit level is not perfectly centered. Accidental errors can be

minimized with a properly maintained and adjusted instrument if the following steps

are taken:

1. Make sure the tripod legs are secure and firmly anchored before leveling the

instrument.

2. Check to see that the bubble is centered before each reading; re-center it if

necessary.

3. Do not lean on the tripod legs when reading the rod.

4. Have the rod person use a rod level, to make sure it is held vertically.

5. Try to keep the line of sight about 0.5m above the ground when positioning

the instrument.

6. Do not use very long BS and FS reading.

b. Systematic / Instrumental Errors occur due to incorrect length of the rod,

when the bubble tube axis is not perpendicular to the standing axis of the

instrument or and when the line of sight of the telescope is not parallel to the

bubble axis. If the line of sight of a level is not exactly horizontal when the

bubble is centered, but slopes either up or down, it will slope by the same

amount for any direction of the telescope. As long as the horizontal lengths of

the BS and FS are the same, from any given instrument position to the rod, the

line of sight will intercept the rod held on each point with exactly the same error

in height. But since one of the sights is a plus sight (+) and other a minus sight

(-), the two errors will cancel each other out in the leveling computation.

Fig.------. When the horizontal length of the foresight (plus) and back sight (minus)

are the same, the systematic error of adjustment of the level is cancelled.

c. Errors Due To Curvature and Refraction

From the definition of a level surface and a horizontal line, it is evident that the

horizontal departs from a level surface because of curvature of the earth. In figure

below, the deviation from a horizontal line through point A is expressed

approximately by the following formula

Cm = 0.0785L2

Where the departure of a level surface from a horizontal line is

Cm is the departure of level surface in meters, and

L is the distance in kilometers

Fig. 5.13. Illustration of horizontal line and level surface departure.

For horizontal sight, refraction Rm in meters is expressed by the formula

Rm = 0.011L2

The combined effect of curvature of the earth and refraction, h is approximated as

hm = 0.0675L, where hm is in meters.

For example, for a 100m length there is about 0.00067m length of error.

BOOKING AND CALCULATION OF REDUCED LEVELS

Two methods are in general used to book and calculate the reduced level; the "rise

and fall" method and the "height of collimation" method. The latter reduces levels

relative to the instrument height. As it has inferior in-built checks it should not be

used and will not be covered here.

Rise and fall method

The rise and fall method uses differences in level between two consecutive points to

obtain the rise or fall in elevation at that point. The "rise and fall" methods shall be

used for reduction of all site levelling. Reduction shall be carried out on site before

packing up to ensure that the levelling has been done correctly. Briefly, a

horizontal line of sight is first established with an instrument called a level. The level

is securely mounted on a stand called a tripod, and the line of sight is made

horizontal. Then the surveyor looks through the telescopic sight towards a

graduated level rod, which is held vertically at a specific location or point on the

ground. A reading is observed on the rod where it appears to be intercepted by the

horizontal cross hair of the level; this is the vertical distance from the point on the

ground up to the line of sight of the instrument. Generally, if the elevation of point A

is already known or assumed, then the rod reading on a point of known elevation is

termed as a back sight reading (plus sight, because it must be added to the known

elevation of point A to determine the elevation of the line of sight).

Calculate the rises and fall between successive points and book them in the

appropriate column (one can determine whether each shot is a rise or fall by the

following rule of thumb: a higher value on top denotes a rise; a higher value on the

bottom denotes a fall) through the following procedures.

1. Add up the back sight and foresight columns for the entire traverse and note

the difference between them; this is the close.

2. Add up the rises and falls for the entire traverse, and compare the difference

between them with the difference between the back sights and foresights;

they should be the same.

3. Carry the reduced levels in the Reduced Level column down the page by

adding or subtracting the appropriate rise and fall values to the successive

values of Reduced Level. The final value of the original starting point will

differ from the original value by the amount of the close.

4. If the levelling has been done correctly and all arithmetic reductions are

correct, the differences between total back sights and foresights, total rises

and falls, and starting and finishing R.L.'s should be the same. This difference

is the close; and for site inspection purposes it should be within ± 2mm or ±

6mm, depending upon which water-level standard is being followed, ± 3mm

or ± 10mm.

For example, suppose the elevation of point A is 200.00 m (above MSL), and the rod

reading is 1.00m. It is clear that the elevation of the line of sight is 200.00+3.00 =

203.00m. The elevation of the horizontal line of sight through the level is called the

height of instrument (HI).

HI=203 4 2 2 1 5

3B D

C

Differential leveling to measure vertical distance and elevation. (a) Step 1: take a Backsight rod reading on point A (b) Step 2: rotate the telescope toward point B and

take Foresight rod reading.

Suppose we must determine the elevation of point B. The instrument person turns

the telescope so that it faces point B, and reads the rod now held vertically on that

point. For example, the rod reading might be 1.00m. A rod reading on a point of

unknown elevation is called foresight (minus sight). Since the HI was not changed

by turning the level, we can simply subtract the foresight reading of 1.00 from the

HI of 203.00 to obtain the elevation of point B,

resulting here in 203.00 - 1.00 = 202.00m.

Checking the Accuracy of Calculations and Booking for rise and fall methodThe difference of the sum of the back sight and foresight should be equal to the

difference between the first and the last reduced levels. If that is the case then,

A

BM 200M

Level station

Back Sight

Fore Sight

Rise Fall Reduced level

Remarks

A 3−

−−

200 BM

B −2

1−

2 202

C −4

5−

−203

3 199

D − 2 2 − 201 End of line

calculation and booking is accurate. Consider the calculation and booking above,

then check for its accuracy.

Sum of Back sight = 9; Sum of Foresight = 8; First Reduced Level = 200; and Last Reduced Level = 201.

Back sight & foresight sum difference = 1 and Diff. between 1st & Last RL = 1Since the difference of the sum of the back sight and foresight is equal to the

difference between the first and the last reduced levels, hence the calculation and

booking of the data are accurate.

COLLIMATION (HEIGHT OF INSTRUMENT) METHODThis method uses the collimation level or height, which is obtained through

calculations of heights of points along a stretch of land. In this method, the back

sight is added to the known elevation of the point to get the height of instrument.

The foresight of the second point is then subtracted from the height of the

instrument to obtain the reduced level or the elevation of the second point. Worked

example of levelling: Consider you are conducting a levelling survey in the

following area portrayed in the figure 1. , where at point D there is a Man Hole then

calculate reduced levels at points A, B, C, D and E, height of instrument at point A is

108.

A B C D E

9 5 6 8

8 6 man hole

Bench mark 100 100 250 300 400

100m

7HI 108

Datum

At A: Reduced level = Bench mark =100

B: Reduced level = 108 – 6 =102

C: Reduced level = (102+9) – 5 =106

D: Reduced level = (106 + 7) – 6 =107

E: Reduced level = (107 + 6) – 8 = 105

The booking of surveying in the figure above is shown in the table below. This

method of booking is called the height of instrument method.

Back sightInter-sight Foresight Height ofInstrument

ReducedLevel

Distance Station Remarks

8.00 108.00 100 0.00 A Bench Mark

6.00 102 100.00 B9.00 111.00

5.00 106 250.00 C7.00 113.00

6.00 107 300.00 D Man Hole105 400.00 E

Checking the Accuracy of Calculations and Booking collimation method

Checking the level’s accuracy for collimation Levels can move out of adjustment so that their line of sight (line of collimation) is

not truly horizontal. This will cause errors in readings which become greater as the

viewing distance increases. However if a back sight and a foresight are exactly

equidistant from the instrument, the error in each sighting will cancel each other

out. This feature can be used to check the accuracy of a level by the following

simple method which is depicted in figure 1. ----------

i. Install three pegs or marks firmly in the ground at distances of 30 m apart in

a straight line; the center peg is only to mark the distance, but the outside

two shall be firm enough for reliable change points.

ii. Set up the level over the center peg and read the staff on each of the outside

pegs in turn. Book these values and calculate the height difference. This will

be a true height difference, as the distances are equal and any errors will be

self-compensating

iii. Set up the level about 4 m to the far side of one of the outside pegs. Read the

staff on the peg 4 m away and then on the one 64 m away. Book these values

and calculate the apparent height difference.

iv. Compare the two height differences; if the instrument is in adjustment (i.e. its

collimation is true) they will be within 5 mm.

The operation of reading a vertical rod held alternately on two nearby points is the

essence of differential leveling. The difference between the two rod readings is, in

effect, the vertical distance between the two points. The basic cycle of differential

leveling can be summarized as follows:

Frequently, the elevations of

points over a relatively long

distance must be determined. A process of measuring two or more widely

separated points simply involves several cycles or repetitions of the basic

differential leveling operation. More specific terms for this are benchmark,

profile, and topographic leveling.

60m Approx.

4m

1.133

1.736

2.217

2.824

Height of Instrument = Known elevation +

Back sight

HI = Elevation A + BS

And

New elevation = height of instrument –

foresight

Elevation B = HI – FS

Figure 1. : A method for checking the level accuracy

1st Set-up: True height difference = 2.824m −1.736m=1.088m

2nd Set up: Apparent height difference = 2.217m− 1.133m=1.084m

Different height = 0.004m.

As long as the difference height between the true and apparent height is less than 5mm, then the level

is in adjustment.

If the instrument's collimation appears to be out, recheck by repeating the process.

Then, whilst setup at one of the outside locations, adjust the instrument (according

to the manufacturer's instructions) so that it reads the correct value on the far staff,

checking it against the near one. Two staves are useful for this.

This type of level check shall be carried out at least once per year, preferably just

prior to carrying out a round of station inspections. The details and results of the

checks shall be recorded in a numbered level book and be readily retrievable as a

quality record, and the date of this calibration check shall also be recorded in the

instrument inventory.

Advantages of Using Surveys

1) Surveys allow researchers to collect a large amount of data in a relatively

short period of time.

2) Surveys are less expensive than many other data collection techniques.

3) Surveys can be created quickly and administered easily.

4) Surveys can be used to collect information on a wide range of things,

including personal facts, attitudes, past behaviors and opinions.

Disadvantages of Using Surveys

1) Poor survey construction and administration can undermine otherwise well-

designed studies.

2) The answer choices provided on a survey may not be an accurate reflection

of how the participants truly feel.

3) While random sampling is generally used to select participants, response

rates can bias the results of a survey.

Exercise 1.0

1.

2. a) What is meant by the term elevation?

b) What does the term leveling mean?

3. What surveying instruments are used to measure angles and distances?

4. a)What is the basic assumption for plane surveying?

b) How does geodetic surveying differ from plane surveying?

5. Under what circumstances is it necessary to conduct a geodetic survey?

6. Give a brief description of the topographic and construction surveying.

7. Why is the proper recording of field notes a very important part of surveying

practice?

8 (a). Briefly describe the following; datum surface, line of collimator, Bench mark

and change point.

(b).The following readings are successively taken with a level “0.355, 0.485,

0.625, 1.755, 1.895, 2.350, 1.780, 0.345, 0.685, 1.230 and 2.150”. The instrument

was shifted after the fourth and seventh readings. Prepare a level book and

calculate the Reduced Levels (RLs) of different points. The RL of the first point is

255.5 m.

9 (a). What is local attraction?

(b). The following bearings where observed in a compass traverse.

Line Forward bearing Back bearing

AB 305000’ 125030’

BC 75035’ 254030’

CD 115030’ 297000’

DE 165030’ 345030’

AE 225000’ 44000’

At which of these stations would local attraction be suspected?

(c). Adjust bearings of the stations affected by local attraction.

10. A distance was taped six times with the following results: 85.87, 86.03, 85.80,

85.95, 86.06, and 85.90 m. Compute the 90 percent error of the survey.

11. a) A group of surveying students measure a distance twice, obtaining 57.455

and

57.350 m. What is the relative accuracy of the measurements?

b). What is the maximum error of closure in a measurement of 2500 ft if the

relative

accuracy is 1:5000?

12. a). Define the following terms

i. Blunder and Error.

ii. Accidental error

iii. systematic error

iv. Closure

v. Relative error

b). What are the basic difference between systematic error and an accidental

error?

CHAPTER 02: MAP READING AND INTERPRETATIONSpecific objectives: By the end of this topic, every student should be able to:-

Explain the concept of map reading and its importance to social economic

activities without teacher’s help.

Identify at least five essentials of a map and its applicability without

teacher’s help correctly.

Recognize features on a map without guide assistance rightly.

Generate information from maps under no teacher’s assistance correctly

Interpret information from the topographical maps in relation to human

daily activities without teachers’ assistance.

Map and its nature

Map is defined as a scaled representation of a whole or part of the earth’s surface

on a piece sheet of paper or wood or any other flat materials. The different maps

can be drawn to illustrate different phenomenon on the earth’s surfaces depending

on its purposes or functions such maps include rainfall distribution maps, vegetation

distribution maps, temperature distribution maps, population distribution maps, and

economic distribution maps showing their corresponding spatial distribution

features. Maps serve as the representation or substitute of any phenomena map

maker wish to portray or study. Maps are directionally and geometrically accurate

due to its ability of showing distance, direction, size and shape in their horizontal

spatial relationship.

The skill of recognizing features and their spatial relationship on the map is called

map reading. Map reading is possible through the conventional symbols and signs

from the key. Therefore, through using these symbols and signs from the key the

process of examining the feature’s characteristics from the given maps is

significantly attained.

Types of maps

There are many types of maps categorized according to their purposes such maps

include soil distribution map, vegetation distribution maps, climatic distribution

maps, population distribution map and so forth. All these map categories are

grouped into two major types which are topographical and statistical maps.

Topographical map is the one which depicts the natural and manmade features of

the landscape with a frame work that resulted from a systematic survey of a

country. These maps show physical features such as mountains, valleys, oceans,

hills, roads, railways, buildings, plantation and so forth while statistics maps show

the distribution of aspects which have been made with the help of exactly statistical

information. Such maps include Isopleths maps, Dot maps, Chloropleth maps and

flowing line maps.

IMPORTANCE OF STUDYING MAPS

Maps help to show the direction of an area

Maps help to portray the geology of an area

CHARACTERISTICS OF MAPS

The map characteristics are marginal information or are essentials of the maps

which are very important in map reading. Cartographer includes these essentials to

assist the whole process of map reading, interpretation and map analysis.

Therefore, these characteristics should be clearly understood by map reader and

map interpreter for accurate reading and interpreting the map.

Title of the map

The title of the map is the word description of what is represented or a brief

summary of map’s content or purpose. The title of the map must identify the area

covered and provide some indication of content, for example KINONDONI DISTRICT,

POPULATION DENSITY IN MBEYA, THE MAP OF KIGOMA SHOWING THE LINEAR

SETTLEMENT ALONG LAKE TANGANYIKA IN 2005.

Scale of the map.

This shows the relationship of the map distance and real ground distance. And the

map information are always affected by the size of scale used to portray them

because the larger the scale the more detailed information while the smaller the

scale the poor detailed information portrayed on the map.. Normally it is difficult to

present the landscape on the paper without considering scale in order to reduce the

ground area. The geographical map scale is approximated to be constant all over

the map. The size of the map scale depends on the size of the land to be presented

on the map, amount of the contents and the size of the map itself.

Hence, Map distance Map scale = Actual ground distance

Types of Map scalesMap scale is often confused or interpreted incorrectly, perhaps because the

smaller the map scale, the larger the reference number and vice versa. For

example, 1:100,000 is considered by some of people to be a larger scale

than a 1:25,000 thing which is not correct. Therefore, there are three map

scales nominated as small scale, medium scale and large scale.

Small scale is one which covers large area on the earth’s surface and shows

much information on the map. The small scale shows large range of

denominator in RF scale e.g.1:250,000. Therefore, the scale contains less

detailed information which leads the shortage of information for particular

phenomena. This scale is used by the cartographer to draw a map if the map

aimed to show very large area such as continents or world which contains

more and less detailed information.

Medium scale on a map covers average area on the ground and shows the

moderate features on the map. The medium scale shows moderate range of

denominator in RF scale. E.g. 1:50,000. Therefore, the scale contains clear

information on the map compared to those shown in small scale.

Large scale is the scale which represents small area on the ground and

shows few features on the map. The large scale shows small range of

denominator in RF scale. E.g. 1:10,000. Therefore, the larger the scale the

more detailed information portrayed on the maps which shows all necessary

information on particular phenomena of the area covered on the map. This

scale is used by geographers to represent the small area of the ground on

the map such as village, district, and regions when they are interested with

just few and more clear details of particular phenomena.

WAYS OF EXPRESSING THE MAP SCALES.

There are several ways of representing scale on map but the major ones are

the Word method (Word or Verbal statement scale) and Fractional

method(Fractional scale or representative fraction ), graphic method(Graphic

bar or line scales), as briefly explained below;-

The word method is one of the ways of expressing scales which is stated in

words. The scale stated in word is termed as verbal or statement scale. In

this way the map distance is commonly represented by centimeter or inch

units and kilometers or mile units for actual ground distance respectively.

For example, one centimeter on the map represents a half kilometer on the

ground or one inch on the map represents five miles on the ground.

Fractional method is another way of expressing map scales where scale

compares map distance with ground distance by proportional numbers

expressed as a fraction or called a representative fraction scale. E.g. the

fraction scale may be in ratio or fraction as 1:50,000 or 1/50,000 and the

former one is preferred. This representative fraction scale can be interpreted

as 1 unit on the map represents 50,000 of the same units on the Earth. In

the representative fraction units are not stated but need to be the same. Any

unit can be used such as mm, cm, inches, feet etc map scale is drawn into

fraction or ratio.

Graphic method is another way of expressing scale through showing a

distance on the map that represents a given distance on the actual ground

by using bar or line. The scale drawn on a straight line is called plain or linear

scale. Normally linear scale has two different units such as meter and

kilometer or inch and mile located in secondary and primary sections of the

line respectively. The secondary and primary sections are separated by zero

where secondary section which is at left hand side of the line shows small

unit for every unit distance such as meters or inches and primary section

which is at right hand side of the same line shows large unit for every unit

distance such as kilometer or feet or miles.

1000m/inches 0 1 2 3 4

5km/miles

Secondary section Primary section

Conversion of map scalesThis refers to the changing or converting scale from one form to another

which will represent the same value. For instance from Statement scale to

Representative Fraction scale or to Linear or from Linear scale to Verbal or to

Representative Fraction Scales and vice versa.

Note. From metric and imperial equivalents

1foot=30cm

1yard=0.9m

1mile=1.6km

1mile=63360inches and

1km=63360/1.6 inches=39600inches

Example1. Convert the following RF-scale into a statement scale;-

a) 1:50,000

b) 2:150,000

SOLUTION

a) Given scale: 1:50,000 this means that 1cm on the map=50,000cm on

the ground.

Assume x be equals to 50,000cm on the ground, then

If 1km=100,000cm from metric

measurement

X=50,000cm

By crossing multiplication,

X= (50,000cm×1km)/100,000cm

X=0.5km=50,000cm

Therefore, 1cm on the map represents 0.5km on the ground.

b) Given scale: 2:150,000 this means that 2cm on the map=150,000cm

on the ground

Assume Y be equals to150, 000cm, then

If 1km=100,000cm from metric measurement

Y=150,000cm

By crossing multiplication

Y= (150,000cm×1km)/100,000cm

Y= 1.5km=150,000cm

Therefore, 2cm on the map represent 1.5km on the ground or 1cm on the

map represents 0.75km on the ground.

Example2. Given the number of kilometer to centimeter or mile to inches,

convert them into RF-scale.

a. 4miles to inches

b. 2km to cm

SOLUTION

a. Given the map scale 4miles to inches

Assume K represents 4miles then,

If 1mile = 63360inches

4miles= K

By crossing multiplication

K=63360×4=253,440inches

Therefore, the RF-scale required is 1:253 440

b. Given 2km to cm

Let X represents 2km, then

If 1km=100,000cm

2km=x

By crossing multiplication

X=2×100,000cm=200,000cm

Therefore, the RF-scale required is 1:200,000.

Uses of map scale.Map scale is used by cartographer and map reader to draw and read map.

Therefore, following are the some useful of the map scale;-

1) Map scale is used to obtain measurements on the mapped area

such as the distance, area and gradient on a map. This enables

the map reader to know the actual size, distance, area and slope

of the mapped area.

2) Map scale helps cartographer to draw maps of the different size

for the same place through reducing or enlarging the map scales

of the area. E.g.1:100,000 to 1:50,000 where 1:100,000 is the

small scale compared to 1:50,000.

3) Map scale helps cartographer to determine the amount of

features to be presented on the map. This is due to reason that

map scale is selective hence only wanted features will be

allocated on the map.

4) Map scale is very essential in the process of map enlargement

and map reduction

A. Date of the map

The date as one of the essential of the map indicates the time spans over

which the information was collected and the day on which the map was

published. Therefore, the date on the map informs the leader how timely or

out of date the map is.

B. Symbols and Signs

These are the different marks purposely to explain the actual object in the

map. The work of the cartographer is to use symbols and signs which will be

easily for the map reader and map interpreter to read and to translate the

information effectively. For instance a green colour stands for vegetation and

purple or white for glaciations region representation. Not all the symbols

which are in the key apply to the particular map but all signs and symbols

applied in the map are shown on the key.

C. North direction

This shows the actual north direction of the map. On the large map three

types of the North printed on top or bottom of the map are Magnetic north

that shows by magnetic compass directed to the magnetic north pole, True

North (TN) is the direction toward the 900 north latitude from any place on

the earth’s surface. The true north represents the lines parallel with the lines

of longitude including 660 called northings. Magnetic North (MN) is the

direction shown by magnetic compass directed to the magnetic north pole.

For example in Africa magnetic north is always to the west of the north. True

North (TN) is the direction toward the 900 north latitude from any place on

the earth’s surface. The true north represents the lines parallel with the lines

of longitude including 660 called northings. Grid North (GN) is the direction

toward the north in those maps drawn to grid system. These maps represent

the lines parallel with the grid north south lines called easting.

Grid North (GN) which is the direction toward the north in those maps drawn

to grid system. For example in Africa magnetic north is always to the west of

the north., True north and Grid north as explained below;-

Consider the figure below.

MN TN GN

`

30055'

30045

Figure1.1

D. Key or legend

Key is the conventional signals that represent certain features on the

topographical map. Key is very important because it helps to summarize the

information of the ground on a map. Map reader and map interpreters use

the signs and symbols on the key to read and interpret the map. For

example

:::::::: Settlement

══ Bridge

V V V V Shrubs

E. Longitude and latitude

Longitudes are imaginary lines measuring the West and East of the great

meridian. The zero longitude is known as Prime Meridian and is passing

Accra and London. Longitude lines are very essential on time location on the

topographical maps.

Latitudes are the imaginary lines measuring North and South of the equator.

Latitude lines are used to fix the position of the features on the map such as

climate, vegetation and so forth.

F. Index number or Serial number

The direction of overseas surveyor’s is responsible for map making and

depicting serial number or index number to show the arrangement of maps

produced and with the totality of maps produced.

G. Margin or Boundary of the map

This shows the boundaries of the area represented on the map. These

margins are sometimes called map boundaries.

Contents and its determination factors on topographical mapsAny topographical map shows three kinds of contents such as natural,

artificial or supportive. Natural contents are non-manmade features

which occur naturally on the earth’s surface as a result of geomorphologic

processes and other natural factors. For example Mountains, hills, forests,

plateaus, rivers, oceans and so forth, while Artificial or Cultural contents

include all manmade features such as infrastructures, settlements, dams and

some artificial forests. Natural forests on maps indicated by names or when

they grow irregularly while that of man-made grow regularly. And also

Supportive Contents on contour maps involve the map marginal information

that assist the map readers and map interpreters. The supportive contents

include scale, north direction, key and date of compilation of the map.

FACTORS THAT DETERMINE THE CONTENTS ON TOPOGRAPHICAL MAPSThe contents of any topographical map is influenced by the factor below;-

a) The purposes of the map which depends on the aims of the

cartographer(map maker) as it is obviously known that not all land

information can be shown on the map as a map show only important

information. Therefore, the aim of the cartographer determines what

information intended to be shown on a map reflecting its purposes.

b) Scale size of the map drawn determines amount and characteristics of

contents to be depicted on the map. This is because map of different

scales show different feature’s characteristics although are drawn from

the same land due to their different map scale sizes. For example if the

two maps are drawn from the same land area by using small scale and

large scale, their contents are likely to differ in such a way that map

drawn from small scale will show many and less detailed features while

of the large scale will show few and well detailed features. Therefore

cartographer can draw a map with large scale in order to show more

detailed information and vice versa is true.

c) Date of compilation refers to a period of time at which a map was

published or produced. It has to be noted that the land information are

dynamic over time due to some factors operating in and on the land

surface. Due to this reason map is likely to show features or

information which were represented by the time when it was prepared

or produced. Therefore, maps drawn at different period of time contain

different information about a particular area. For instance, the dares-

Salaam maps published in 1940sa and 1980s show different features.

The Dares-Salaam map drawn in 1940s cannot show TAZARA railway

and MANDELA road while that of 1980s show these features.

d) Nature of the landscape also determines the nature of the contents to

be illustrated on the map. Maps represent different nature of the

landscapes show different information due to their spatial distribution.

For instance, a map of Tanzania is drawing to show only two regions

Kigoma and Dares-Salaam show different contents in such a way that

Kigoma map must show Lake Tanganyika while that of Dares-Salaam

must show Indian Ocean although all these are water bodies but they

differ in their names, size and other characteristics.

e) Cartographer(map maker) nationality determines the contents on the

map, if the two maps of the same area are drawn by the two people of

the different nations their contents differ in such a way that map drawn

by foreigner lack some important features because of being not

familiar with the mapped area.

MEASUREMENTS ON TOPOGRAPHICAL MAPS

Distance measurement on the topographical maps

Distance measurement between the two or stations on the map is only

possible if the map scale is well stated. The map reader can measure the

distance of the points by using pair of dividers, piece of edge of paper or a

length of thin string (thread). All measurements must be converted into

ground distance by using the map scale provided. And the following are the

some of the tools uses to measure the distance between the two points;-

i. Pair of divider is common method that used to measure a short and

straight distance (linear distances) between the points on the map.eg.

Short straight road and railway on the map can be measured by pair of

divider.

ii. A length of thin string (thread) is used to measure a stretch with many

curves or bends (nonlinear distances) on the topographical map.

iii. A piece of edge of paper with a straight edge can be used to measure

both linear and nonlinear distances on the map. Under this method a

map reader marks on every corner between the distances on a white

edge of paper by using well sharpen pencil.

iv. Transfer the recorded distance on a ruler and then the map distance in

centimeters.

v. Convert the map distance into actual ground distance by using the

formula,

Map distance Map scale ═ Actual ground distance

vi. Convert the real ground distance in either Kilometer or any other unit

as you restricted

For example, carefully study the sketched map given below and then find the

distance of road from KIGOMA STATION to Kasulu via KIDAHWE and KIGOMA

STATION to MNANILA in km.Border Kasulu

KIGOMASTATION 1:250,000

We have given;-

Map scale=1:250,000

uvinz

a

Road

Mwang

a

Centre

Ujiji

Kid

ah

we Uvinza road

MnanilaBuhigwe

Map Distance measured on the road from KIGOMA STATION to

Kasulu=25.3cm

Map distance measured on the road from KIGOMA STATION to

MNANILA=18.9cm

From,

Map scale ═ Map distance Actual ground distance

Let actual ground distance from KIGOMA STATION to Kasulu be equal to P,

then

1 ═ 18.9

250,000 P

By crossing multiplication

P=250,000×25.3cm

=6325000cm, then convert into km.

If 1km=100,000cm

P=6,325,000cm

By crossing multiplication

P=63.25km

Therefore, the distance from KIGOMA STATION to Kasulu is approximately to

be 63.25km

And let the actual ground distance of the KIGOMA STATION to MNANILA be

equal to K, then

1 ═ 18.9cm

250,000 K

By crossing multiplication

K=250,000×18.9cm=4,725,000cm

If 1km=100000cm

K=4725000cm

By crossing multiplication

K=47.25km

Therefore, the distance from the KIGOMA STATION to MNANILA is 47.25km

AREA MEASUREMENTS ON TOPOGRAPHICAL MAPSMeasurement of an area on a topographical map can be estimated

depending on the shape of the map or feature to be estimated as follows:-

a) Regular shape feature such as triangles, rectangles and circles can be

estimated by using their mathematical formulae. This method of

estimating the area of regular features is called Behaviours

Geometrical Shape.

The figure can be divided into three regions of a, B and C where a is

rectangle and B and C are Triangles

To find the area of the rectangle, first measure the length and width

and use the formula of rectangle,

Area of a rectangle ═length ×width

To find the area of the triangle Band C measure their bases and

heights and then uses the formula for each triangle

Area of a triangle ═ Base × Height 2

The total area of the figure above area ═ of the rectangle+ area of the

triangles and then convert the sum of the area obtained due to the

given map scale either in Km2 or miles2.

b) Irregular shape features in topographical maps are so common and

cannot make easy estimation of area by using the mathematical

formulae. These include the shape of lakes, islands, forest, plantation,

settlement etc. The area of irregular shape features on the map is only

possible under strip and grid or tracing or square methods.

i. Stripping method

Striping method is the method used to calculate the area of irregular shape

features by performing the following procedures;-

1. Trace the shape of the feature on which its area is to be calculated or

estimated.

2. Draw the strips of homogenous width to cover the whole mapped area.

3. Measure the length and width of each strip

4. Calculate the area of each strip by using mathematical formula

(Rectangle formula) and then convert the area obtained due to the

map scale provided.

For example, consider the topographical map below and then calculate the

area of coffee estate in km2.

1:50,000

Figures 1.7

Area =length ×width where, width=1cm, then

Strip1. Area =7cm×1cm=7cm2

2. Area =8cm×1cm=8cm2

3. Area=8cm×1cm=8cm2

4. Area =6cm×1cm=6cm2

5. Area=6cm×1cm=6cm2

Total area =35cm2

From the map scale given, 1cm on the map=0.5km on the ground, then

1cm2 on the map will be equal to 0.25km2 on the ground.

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Let the actual area of the coffee estate be N, then

If 1cm2=0.25km2

35cm2=N

By crossing multiplication

N=35×0.25km2=8.75km2

Therefore, the actual area of coffee estate is 8.75km2.

ii. Grid or tracing or square method

This is the simplest and commonest method of estimating the area of

irregular shape features by performing the following procedures.

1. Identify the figure of the map provided carefully.

2. Mark complete and incomplete squares of the mapped features.

3. Calculate the area of a square in its units, and then convert it due to

the map scale given

Use the formula

Total area═ (complete squares+ incomplete squares) ×area of a grid.

2

Example, Consider the figure provided below and then calculate the area of

KAIZE sisal estate in km2 as roughly shaded in February 2008.

KAIZE SISAL ESTATE IN 2008

1:50,000

SOLUTIONS

DATA GIVEN: Complete squares = 34

Incomplete squares=75

Width and length of a square=1cm by 1cm then,

Area of a square =length × width

=1cm ×1cm=1cm2

From map scale given, 1cm on the map=50,000cm on the ground

1cm on the map =1/2km on the ground

On squaring both sides, 1cm2 on the map=1/4km2 on the ground.

Then, area of a square= 1/4km2

Area of the sisal estate ═ (complete squares+ incomplete square) ×area of a square

2

═ (34+0.5(75)) ×1/4km2

═71.5x0.25km2=17.875km2

Therefore, the area of sisal estate is 17.875km2.

Methods of fixing the position or location of the features on the topographical mapsA map reader as well as interpreter has to use Latitude and longitude, Grid

reference system, Place name or Bearing and Direction to determine the

position of the features on the topographical map. These are four ways used

to fix the position features on the map.

LATITUDE AND LONGITUDE Latitude is defined as the angle between the perpendicular to the surface

and the plane of the Equator (greater circle) to that place. There is 1800of

latitude from pole to pole. The quadrant of the equator from each pole is

divided to 900. The numbering start from the equator 00 and goes by degree

minute, second to 900at the pole. Latitude is designated as north or south

latitude e.g. 300N. Latitude lines are the imaginary lines measuring North and

South of the equator.

The longitude of a place is the arc, measured in degree, of a parallel

between that place and the meridian. The angular distance of the degree

meridian provides the east-west distance. Longitudes are infinite set of

greater circles or meridians arranged perpendicular to the parallels. Unlike

the latitude, no meridian has a natural basis for being the starting line to

determine the distance east west in degrees, minute, seconds of longitude.

From a given meridian, selected as a starting line, east-west position is

designated by angular distance along the parallel circle in the latitude

system. Therefore, the length of a degree longitude become shorter with

increasing latitude until becomes 00 at the pole.

Grid- reference systemGrid system is a pattern of horizontal and vertical lines forming squares of

uniform sizes drawn on a map to aid in fixing the position or location of

geographical features. The number running east to west along the top to

bottom of the horizontal lines drawn on the map are called eastings and

those running from south to north along the right and left margins of the

vertical lines drawn on the map are called northings. Grid reference is the

reading in a grid system which contains four or six figures printed three

figures as eastings and other three figures as northings for the case of the

six figures and two figures for eastings and northings for the case of the four

figures (numbers).

For example, Study the sketched map provided below and then answers the

question that follows:-

569 570 571 572 573 5 74 5 75 576 577 578

922 TANAPA office Telephone offices

92 921

921 920 ware houses

920 kite hills 919

918

918 917

917 916 market

916 915

915 914 Cultivation

914 913 sch

913 912

Prison 912 911

Tanesco 911 910

910 569 570 571 572 573 5 74 5 75

576 577 578

1:50,000

1. Name the grid-references for the location of following features:-

a) Telephone offices

b) TANAPA office

c) Top of Kite hills

2. What are the features found at the following grid references?

a) 693 194

b) 765 120

c) 729 190

3. Calculate the length of the road from the grid reference 710 000 to

730 225.

4. Calculate the area of cultivation to the south east of area covered on

the map in kilometer squares.

Place name.The place name is another way of fixing the position of an area represented

on topographical maps. In this method name like Kigoma, Kondoa, Dares-

Salaam and so forth are clearly marked on a map. The place located should

be meaningfully to the person who is located it on the map and map reader.

Therefore, a small and unpopular part of the town should not be shown on

the map because it is not well known to the most of the people. The place

name must described clearly in order to avoid some confusion , for example

many places have the same name, the only way to avoid such confusion is to

add distinguishable items and also information about the situation of the

particular places that are intended to find the differences.

Revision exercise 1.0

1. Convert

a. 1:50,000 into statement scale if it is given in inches to miles.

b. Linear scale into statement and RF scale

1000 M 0 1 2 3 4 5KM

2. List at least three significances of the map scale.

3. Which one of the following aspects is not true about map reading?

a. Map reading is concerned with recognition of features and their

spatial distribution on the earth’s surface

b. Map scale is concerned with the ratio between the map distance

and ground distance

c. Line is the method of expressing scale on the map

d. Stripping method is the area method that considers the full and half

squares in calculating the area on a given map

4. Choose the small scale among of the following map scales.

a. 1:50,000

b. 1:250,000

c. 1:100,000

d. 1:10,000

5. Define the following terms:-

a. Map

b. Map reading

c. Map scale

6. List any five common characteristics of the maps

7. Briefly explain ways of expressing scale on the map

8. Give the reason, why is it important to use the following aspects in

map reading?

a. A key

b. Title

c. North direction

9. Contrast forward and back bearing as used in map reading.

10. Carefully study the map extracted from Kigoma sheet 92/3 and

then answers the following questions:-

a. Calculate the area covered by the forest in kilometer squares.

b. Find the distance of the railway from Docks to Uvinza in

kilometer.

c. Convert the linear scale given into the statement scale.

d. Calculate the bearing and direction of Katosho Lake from Bangwe

point grid reference 879582.

e. Identify the main features found in the following grid

references:-

i. 895621

ii. 885571

iii. 003629

iv. 93462

THE GRADIENT OF AN AREA ON CONTOUR MAPS

The gradient is the steepness of an area that shows the extent to which the

land is inclined. The gradient of an area is obtained by taking the ratio

between the vertical increase which is difference between the highest and

lowest contours (amplitude of contours) and horizontal equivalent which is

the distance of the slope of an area. And always the gradient is expressed in

ratio form where numerator must be equal to one.

Thus,

Gradient ═ Vertical Increase (interval) Horizontal equivalent

Where: The vertical interval=Highest Contour─lowest Contour and the

horizontal equivalent is worked out by converting map distance into actual

ground distance through map scale given. Therefore, horizontal equivalent is

equal to ground distance and should be written in meters.

Steps of finding the gradient of an area

The following are three major steps of obtaining the gradient of an area

Find the vertical increase V.I between the two points by taking

contour’s amplitude such that

V.I=Highest Contour−Lowest Contour

Measure the horizontal distance between the two spots on the map

and then convert it to the ground distance by the map scale.

Calculate the gradient of the between the two spots by using the

formula

Gradient = Vertical Increase Horizontal Distance

NOTE: The unit of both vertical and horizontal distance must be same.

For example, find the gradient of the road from point A to point B if the map

scale is 1:50,000

550

A B 600

200

150

100

50

We have given that: Highest contour =600m

Lowest contour =50m

Map scale =1:50,000

Measured map distance from point A to B=11.8cm

From,

Gradient= vertical increase Horizontal equivalent

Where, vertical increase=Highest contour- Lowest

contour

=600m ─ 50m=550m

Horizontal equivalent = actual ground distance

= Map distance Map scale

= 12cm = 600000cm=6000m 1:50,000 Then, Gradient = 550m = 1 6000m 11

The gradient of the road between point A and point B is 1 in 11. This

indicates that for every unit step vertical rises there are 11horizontal steps

rise.

Example2, the highest contour between the two towns is 18000m and that of

the lowest contour is 550m. Find the steepness of the area if the ground

distance is 25km.

SOLUTION

Data given: Highest contour=18000m

Lowest contour=550m

Ground distance=25km=25000m

From,

Gradient= vertical increase Horizontal equivalent

= Highest contour-Lowest contour Ground distance

= 18000m-550m

25000m

= 1 1.4

The gradient is 1 in 1.4. This indicates that for every 1 vertical step rises there is 1.4 horizontal steps rise.

Contour maps and Land forms Land forms are the reliefs such as all the natural rocky features on the

surface of the earth. The term ‘‘land form’’ is applied by physiographers to

each of the multitudinous features that taken together make up the surface

of the earth. It includes all broad features such as plains, plateaus, and

mountainous and also all the minor features such as hills, valleys, slopes,

canyons, arroyos and alluvial fans. Most of these features are the product of

erosion, but the term also includes all land forms that result from the

movement of the earth on the earth’s surface and from movements within

the crust of the earth. The relief features or land forms on topographical

maps are recognized by looking the patterns of the contours. But these land

forms shown on contour maps may be grouped as high land forms and low

land forms which include plateaus, hills, ridges, spurs, slopes, escarpments,

passes, saddle or col and water shed and Levee ̑s, v-shaped valleys, gorges,

floods and delta respectively.

High land forms on contour maps

a) Plateaus defined as an extensive upland area with steep slopes and

flat of fairly level surfaces on the top of the surface. On the contour

maps plateau is recognized if there is the presence of roughly circular

contours, but the last highest contour round a large space on the map

and form the shape of the slope of the plateau sides. Consider the

figure below.

650

750 850

Figure. A plateau

b) Hills as a rounded upland not as High Mountain, on the map hill is

recognized by the presence of the roughly circular contours closed

together. A hill is below 500m high.

850

800

750

700

650

850

800

750

700

650

Plateau

210

180

Hills

360

M M

360 360

330 330

300 300

270 270

240 240

210 210

180 180

Figure

c) A ridge is a big narrow and long upland with steep slope. The contours

of a ridge close and form an elongated rough circular. Because the

land is long and narrow and rises rapidly, the l contours are elongated

and very close to one another.

85

135

435

Meters

Meters

435

435

385

385

335

335

285

285

235

235

185

185

135

135

85

85

d) A spur is a projection of land or a broad tongue like structure of the

land from the side of a hill or mountain towards the valley. The

contours of the spurs form the V- shape that points down low land.

7

6

5

4

3

2

1

Meters

Meters

7

7

6

6

5

5

4

4

3

3

2

2

1

1

Figure A spur

e) Slopes which are slanting piece of land. The slope of an area is

steepness of an area and can be categorized into four categories ;-

1. Steep slope is slanting land which is very steep at both top and

bottom of the slope. Steep slope is recognized on the

topographical maps when contours close one to another every

spaced from the top to the bottom.

Figure

2. Concave slope is the slanting land which is steep at the top and

gentle at the bottom. It is recognized when contours close

spaced at the top and wide spaced at the bottom of the slope.

3. Convex slope is slanting land which is gentle at the top and steep

at the bottom. It is recognized in contour maps when contours

wide spaced at the top and close spaced at the bottom.

4. Gentle or regular slope is slanting land which is gentle at both

top and bottom of the slope. Gentle slope is obtained on contour

maps when contours wide or even spaced from the top to the

bottom of a slope.

f) An escarpment which is an upland that have gentle slope on one side

and steep slope on other side. On contour maps escarpment is well

recognized if there are very close roughly circular contours observed to

one side and widely spaced contours at another side of the slopes.

g) Water shed is a line of upland dividing the head water of two streams

or two drainage basins. On contour maps water shed is recognized if

the highest contour of water shed area run parallel to each other and

this is due to the presence of the two rivers dividing to different

directions.

Low land forms on contour mapsa) Levees are natural embankment built up by a stream along the edges

of its channel. In contour maps the embankments are shown by packed

lines at right angles to the course of the river.

b) V-shaped valleys, in the upper course the dominant work of a river is

vertical erosion. The river cuts a steep sided v- shaped valley. The

contour lines of a v- shaped valley form V that point up stream. The

stream crosses each contour at highest point of each V. when the v-

shaped is narrow and the contours are closed, indicates a narrow steep

valley and when the V- shape is wide and far apart indicates a wide

and less steep valley.

c) Gorges are deep narrow steep sided river valley. The contours of a

gorge close together forming a narrow V- shaped pointing sharply

upstream. The river in the gorge crosses each contour at the highest

point of each V.

d) Flood plain is an area of low land built up by the deposition of alluvium

(alluvial materials). During flooding the rivers floods the low land and

spreads a layer of silt over the flood plain. The contours of flood plain

run roughly parallel to the main river and the lowest contour is spaced

I a way that it mark the general width of the flood plain. The other

higher contours are evenly spaced marking the gentle slope of the

banks of the plain.

e) Deltas are the flat area of alluvial materials at the mouth of river

crossed by many distributaries that enter a lake or a sea. The lowest

contour marking the delta follows roughly the outline shape of the

delta.

Maps and Cross Section or Relief SectionCross or relief section is defined as a geological diagram or actual field

exposure showing the geologic formations and structures transacted by a

given plane. Cross section diagrams are commonly used in conjunction with

geologic maps and contribute to an understanding of the subsurface

geology. Properly done, the map is an exceedingly important tool in

geology. The graphical picture it gives of the location, configuration and

orientation of the rock units of an area could be presented in no other way.

Essential as the map is, however, it is not without limitations, and if it is to be

of maximum use these limitations must be fully understood. The most

important point to realize is that geological maps generally record both

observations and interpretation. In part, the element of interpretation is due

to a lack of time and complete exposure; it is almost never possible to

examine all parts of an area. If a complete map is to be produced, this lack

observed continuity then requires interpolative between observation points

and such interpolation is, to a greater degree or less degree interpretive.

Factual and interpretive data on a map may also be distinguished by

considering the two aspects more or less separately. An out crop map is one

of presenting field observations in a more objective way and another way of

conveying the essential information of an out crop map, but without actually

drawing in the boundaries of the exposed rock masses, it to show abundant

attitude symbols, which then serve two functions: to record the measured

attitude and to mark the locality where the attitude can be measured.

Vertical structure sections, though they have their limitations, also useful in

helping to work out and depict the structural relationships at depth,

particularly when the structures are diverse and no single down structure

direction exist. The formations, faults, veins and so forth, are shown by

convectional symbols or colours, and the scale is adapted to the size of the

features present. Unless otherwise noted, cross sections are drawn in

vertical plain. The profile shows the relief variations of the landscape such as

mountain, valley, depression, and so forth on contour maps. The relief

section is drawn to illustrate the exposed geology of an area under the

following procedures:-

1. Identify the two end points that are to be sketched on a contour

map, and then draw a straight line on the map to join them.

2. Lay down a straight piece edge of paper along the drawn straight

line and on it mark:-

i. Points of intersection of the topographic contours and the

sections

ii. Features such as the crests of hills, saddle, ridge, vegetation or

the location of streams should also be marked even though a

contour line is not present.

iii. The elevation of the contours must also be indicated; every

contour may be marked especially if they are widely spaced or if

closely spaced, only those which mark change in slope direction

may be used.

3. In constructing a frame work of drawing the cross section attempt

the following procedures:-

i. A series of elevations lines are then drawn on a second sheet of

paper with spacing equal to the contour interval and plotted at the

same scale as the map.

ii. The topographic points along the section line are then transferred

from the edge of the marked paper, which the now represents the

line of section, by projecting the contour marks to the

corresponding elevation lines.

iii. Each of the points located is joined with a line representing the

topography. And if the spacing of the contour lines is wide, the

map may have to be consulted to assist in sketching in

topographic details.

iv. Choose the vertical height by examining the contours along the

line of cross section and then deal with the lowest and highest

contours as quick as possible. If the lowest contours start from

non-mean sea level take it as it is and not assume that all lowest

contours start from mean sea level and marked by zero meter as a

starting attitude.

4. Finishing the cross section through making it net, accurate, simple

and legible. And then mark and label the required informational

features.

5. Shade the relief section; put a heading, key and vertical

exaggeration (VE) to determine the size of the vertical scale times

the horizontal scale.

Vertical Exaggeration (V.E) It is very common practice to draw cross section with the vertical scale

enlarged relative to the horizontal scale; that is, to stretch the section

vertically while leaving the horizontal dimension un altered. The vertical

exaggeration of a map is a change in a model surface or profile created by

proportionally raising the apparent height of all points above the base level

while retaining the same base. It is enlarging the vertical component on a

profile, relief model, or a block diagram to make it more apparent. This

practice is especially common I sections showing stratigraphic or geographic

information where more space is needed to plot vertical details or to

accentuate certain features which would others be obscure. The result is

known as a vertically exaggeration section, and the degree of stretch is

defined by an exaggeration factor V,

Vertical Scale V = Horizontal Scale

Example1. Given that the cross section has a vertical scale of 1cm to

250m and a scale of a map is 1:50,000. Calculate the vertical

exaggeration.

SOLUTION

Data given: vertical scale=1cm: 250m=1:25000

Horizontal scale =1:50,000

From the formula;

Vertical Scale Vertical Exaggeration =

Horizontal Scale 1:25,000 = = 2.0

1:50,000 The vertical exaggeration is 2.0, which indicates that the vertical scale is

twice the horizontal scale.

Example2. Given that the relief section has a horizontal scale 1:50,000 and

vertical scale 5km, calculate vertical exaggeration.

SOLUTION

Data given: horizontal scale=1:50,000

Vertical scale =5km=500,000cm = 1:500,000

Vertical exaggeration= Vertical scale Horizontal scale

= 1:500,000 = 0.1 1:50,000 The vertical exaggeration is 0.1, which indicates that the vertical scale is one

tenth times the horizontal scale.

Intervisibility between the two spots on contour maps.Intervisibility is an ability of one spot to be seen from another spot. A good

way of determining if the two spots are intervisible on the map is to draw a

cross section from one point to another to view the structural appearance of

landscape in between the given two spots (points). If the two points can be

seen each one from another, then the two points are said to be intervisible

otherwise is non intervisible. This is possible if there is no raised ground in

between but if however, there is a raised ground in between, then they will

not be intervisible.

Usually on a cross section, draw a straight line called sight line to connect

two end points and if the line passes in between the points it implies that the

two points are intervisible and if the line is obstructed in between the two

points, this implies that there is no Intervisibility. Consider the figure below shows

points A, B and C

B

Line of sighting C

A

Figure.

Comment: Points A and C are not intervisible due to the presence of raised

ground that obscured the line of sighting while Points B and C are intervisible

points because there is no obstruction between them. Generally

Intervisibility is affected by the presence of relief features like mountains,

hills, vegetation like thick forest, building in between of two points that

obscure the two points.

For example, given the map having contour lines, as shown below whose

map scale is 1:50,000. Construct cross section from point A to B to the relief

features and then comment on Intervisibility between the points.

Scale; Vs: 1cm=250m

Hs: 1cm=500m

A 1250 1400 1550 1450 1450

1300 B

Meter

Meter

1600 1600

1550 1550

1500 1500

1450 1450

1400 1400

1350 saddle 1350

1300 1300

A1250

1250 B

Figure

Vertical Scale Vertical Exaggeration =

Horizontal scale

1:25,000 = = 5.0 1:50, 000

Therefore, vertical exaggeration of the area mapped is 5.0 which means that

the vertical scale is five times the horizontal scale of the map.

There is no Intervisibility between the two points A and B, because point A

cannot be seen directly from point B due to the presence of two raised

grounds (hills) between them.

Significances of Cross Section1. It provide a clear pictorial view on the structural appearance of an area

between the two spots

2. It is used in Intervisibility determination of an area

3. It shows clearly the altitudes of different part of the land between the

two spots

4. It aid to make gradient determination of a slope landscape by relating

the vertical intervals to horizontal equivalent.

Methods of Determining Relief and Relief Features on the contour MapsThe relief of an area is the surface form of the land surface which shows size, shape,

slope of the high land and low land. Relief shows the land forms on the earth’s

surfaces which differ in shape and size. These land forms are referred to as relief

feature, good example of relief features are crater, caldera, mountains, hills,

plateaus, valleys, ridges, inselberges, spurs, flood plain, escapement, river basin

and so forth. Relief features on topographical maps are shown by using different

ways (methods) include the following;-

TRIGONOMETRICAL STATIONThese are the points on topographical maps with their exactly height fixed usually

from the sea level on mountain peak or other visible points. These trigonometrical

points are marked by a triangle followed by the number of the height of the land.

The method has merits and demerits like other method and the following are

the some of the merits and demerits of this method.

Merits of trigonometrical stations

The trigonometrical points show the actual height of places on a mapped

area. These points are marked on the ground by a concrete pillar, a slab or a

stone, in locations that offer the maximum view of a given area.

Trigonometrical stations are indicated on maps by special symbols as shown

below and hence easy to read and interpret, for example

--------Indicates the highest altitude

------Indicates the lowest altitude

Demerits of trigonometrical stationsThe method does not show the nature of the landscape features like size, shape,

slope of the land forms and so forth since shows only height of the landscape. The

method is not used to identify land forms like hills, mountains, valley, depression

and so forth. It needs some training since it involves special symbols to read and

interpret them.

SPOT HEIGTHThis is the topographical method of showing relief of a mapped area indicated by a

dot with their exactly height above a known level such as from sea mean level. On

topographical maps spot heights are represented by a dot and height actually is

written beside. And on the ground spot heights are marked on a permanent plot like

rock

1825 which means that 1825m is above mean sea level.

CONTOURING METHODContours are the line drawn on the map to join all points of the same and

equal heights above the sea level. The measurement of the heights shown

by contours lines start from mean sea level which is regarded as zero height.

The mean sea level is the average level between the high and low tide

marks. Contour lines are drawn on a map at intervals of the same numerical

value known as the vertical interval or contour interval. Thus, the vertical

interval of contour is the difference between the two successive contours.

Characteristics of the method

i. Contours are drawn at a fixed interval called contour interval (c.i) or

vertical interval (v.i).

ii. Contour are numbered in the breaks or above the line to the high

ground

iii. Contours never cross one another

iv. Contours which are drawn closely suggest steep slope while contours

drawn widely spaced indicate gentle slope. Consider the figure below

A B

Figure

Region A has steep slope because horizontal distance from one

contour to another is smaller than that of side B, hence on side B there

is gentle slope compared to side A due to the large horizontal distance

between the contours.

Advantages of the method

The method shows the accurate height of the land forms and their nature for

example slope, shape and size of the land forms. The method maybe

combined with other methods of representing relief such as spot height,

trigonometrical station and layer colouring method without interference.

Reading and interpreting relief on the map by using contours is very easy

since contours show shape of land forms.

Dis advantages of the method

In modern maps where more contours apply lead confusion to the map

reader and map interpreter during the map reading and map interpretation

of features from the mapped area.

FORM LINESThese are the lines drawn on a map joining points of approximately the same

height above the mean sea level. These lines are drawn by estimating the

height of the land with the help of spot height.

Characteristics of the method

1) Form lines are usually un numbered lines drawn on a map to join

nearly the same heights

2) Form lines have no fived height interval

3) Form lines are broken line

4) Form lines can sometimes cross each other

5) Form lines apply where the contours do not apply

Figure

Advantages of form lines (method)

Form lines apply where contours failed to work to show the nature and the

shape of the landscape so, they are used as substitute to contours. Form

lines combine with other method of the relief representation such as

colouring method.

Dis advantages of the method

Form lines do not indicate the accurate height of the land form from above

mean sea level and do not apply where contours work to show relief of an

area.

HACHURESThese are short lines drawn to represent the direction of the slope of land.

Where the slope is steep, the lines are thick and close together, but where

the slope is gentle, the lines are thin and wide apart. And if the area is not

hachured the land is said to be flat.

Advantages of hachuring

method

Hachures provide an idea about the general relief of an area such that steep

slopes can be distinguished from gentle ones. Hachures together with

contours can also be used to show minor but important details on maps,

where such details would not have been shown if contours were used alone.

Also, on modern maps hachures are sometimes used alongside contours to

show minor features such as road cutting, railway cuttings or small craters.

However, hachures are not very common on modern maps.

Disadvantages of hachuring method

If hachures alone are used to show relief, the map would lack definite

information about the height of the land above the sea level. Hachures do

not provide the exactly height of an area above the sea level. Hachures

require a lot of time to draw and to add information for showing various

features, such as areas covered by the vegetation, crops or settlements is

more difficult to insert either in writing or drawing without interfering with

the hachures. And more closed hachures hide some minor and important

features covered on particular area shown on a map.

HILL SHADING METHOD

This method uses light to illuminate some parts of the map while casting

shadow over others. In this method, there are two techniques are used to

express this;-

1. Assume light is shining vertically above the land.

In this technique the steepest slopes are least lit while hill tops, surface

of the plateau and plains as well as valley bottom are well lit. The least

lit areas have a darker shade while the well-lit areas have a lighter

shade.

2. Assume the light is shining over the land from the north-west direction.

In this technique the slope facing north-west and east and south have

dark colour. Varying shades of

Colours are usually used.

SUN

Figure

Advantages of method

1) Hill shading is commonly used on Atlas maps showing relief, hence it

gives an idea about the general relief of an area.

2) It is easy to read and interpret map since diagram is used to illustrate

features

3) It combines with other method of relief representation such as

hachures and layer colouring methods.

Disadvantages of the method

1) Hill shading does not indicate the accurate heights above the sea level

2) The insertion of more details is difficult in the darkly shaded areas

3) It is also difficult to determine the direction of slope as well as the type

of land forms on the map

LAYER COLOURING AND HYPSOMETRIC SHADING METHOD

This is the method of showing relief by using colour or tint or some form of

shade (hypsometric shading). Land within a certain range of altitude is given

a particular colour or shade. A single colour example brown with varying

tones may be used. The faintest tin usually represents the lowest land and it

becomes progressively darker with increasing altitude. On the other hand, a

set of carefully chosen colour can be used to represent land within each

range of altitude as shown below.

Colour HeightWhite Over 5500mPurple 3600-5500mBrown-purple 2700-3600mDark brown 1800-2700mLight brown 1400-1800mBrownish –yellow 900-1400mYellow 400-900mLight green 180-400mGreen 0-180m

Each tint merges into the next one to show continuity of relief

Advantages of the method

1) Both hypsometric shading (lines) and tints used to depict the relief

of an area, as they use uniform colours and only vary in

concentration accordingly. (see the illustration below)

Figure

2) On modern Atlas both layer tinting and hypsometric shading may be

used in the same maps. The variation in depth of colour or shade is

maintained for both.

3) Layer colouring and hypsometric shading are useful in showing the

distribution of high and low grounds at glance.

Limitations of using this method

Layer tinting is only suitable for a region of varied relief and therefore, it

cannot serve any purpose to tint a whole region covered on the map with

only one colour if such region is almost level. It can mislead to tint or shade

by one colour assumes uniformity of height and yet the land is usually

steadily rising. The method is equally difficult to estimate heights of specific

places if tinting or shading work. It is difficult to identify land forms on such

maps where concentration of colour applies to tint or shade. In regions of

high altitude, the tint or shade may be so dark that insertion of additional

information becomes impossible. Also, it is very expensive to tint or shade a

large area covered on the map by using different colour.

PICTORIALS METHODThis is the method of showing relief using drawings of land forms. Picture of the

land forms such as hills, mountains and valleys are drawn on a map in the

approximate positions where such land forms are to be found.

Figure

Advantages of the method

The method was used on ancient maps especially those used by explore

even though such maps are not common now days. Also, pictorial are easy

to interpret because the type and shape of the land forms can be easily

determined.

Dis advantages of the method

The symbol used is viewed from an angle which is contrary to the idea that a

map is supposed to be viewed vertically from above. The pictures may

obscure the details and therefore, some important details may not displayed

on the contour maps. Pictorials do not give heights of land above sea level as

it is difficult to draw the symbols in proportion to their various heights or

depths. Also, only a limited variety of land forms can be shown by using this

method.

BENCH MARKA bench mark (BM) is the term given to a definite, permanent accessible point of

known height above a datum to which the height of other points can be referred. It

is usually a stainless steel pins embedded in a substantial concrete block cast into

the ground. At hydrological stations rock bolts driven into bedrock or concrete

structures can be used, but structures should be used warily as they themselves are

subject to settlement. The locations of benchmarks shall be marked with BM marker

posts and/or paint, and recorded on the station history form.

MAP INTERPRETATIONMap interpretation is an ability of translating the signs and symbols to examine the

given geographical information on an area covered on the map. These information

includes climate, relief, economic activities, drainage, and transportation networks,

vegetation distribution, settlement distribution, water bodies and other features.

The interpretation of physical features and human activities on topographical maps

directly involves the study of relief and relief features on the area covered on the

map. But the land forms and other features can be easily identified and interpreted

only if their physical appearance and conventional signs are well known, for

example

─ Church (chi) ─Mosque (mosq), signs for religious affair.

− Sign for scrubs (scattered trees)

The objectives of interpreting physical features and human activities on

topographical maps are achieved if Interpreter use compass points, grid

reference and physiographic regions or relief regions such as high lands,

escarpment, low lands, plains and so on to interpret the location or position

of the physical features and human activities. Interpreter must master the

correct phrases that should be used in the interpretation of physical

features and human activities on topographical maps. The following are the

important phrases:-

i. To the north –east of the area covered on the map

ii. To the west of eastings of the area covered on the map

iii. To the south of northings of the area covered on the map

iv. On the high land or low land of the area covered on the map

v. On the plain of the area covered on the map

vi. On the escarpment of the area covered on the map

vii.On the ridge of the area covered on the map

Avoid phrases such as “to the east of the map” since the map is just a piece

of paper. Instead use the phrases “to the east of the area covered on the

map”. Also avoid using phrases such as “to the bottom of the map” or “to

the top” or “to the left or right of the map”. Whenever there is a describing

of a certain feature on a map such as vegetation, settlements, and swamps

always refers to the key in order to ensure that the features described are

correct.

Interpretation of relief on topographical mapsRelief refers to the physical appearance of an area by its land forms of

contrasting shape and size. We interpret the relief of an area from a

topographical map by observing the arrangement of contours and their

respective heights. It is very important to find out from the key whether the

heights are in meters or feet. In common, relief of an area can be of either

highland or low land.

High land relief

The relief of high land is recognized if the contours on a map show higher

number of elevation of above 500m from the mean sea level. Relief of the

high land is varied and can be either mountain highland or plateaus where

the mountain high land is recognized if the map shows many hills or summit

dissection of rivers (streams), the presence of pass, saddle, watershed and

escarpment. State the types of hills, whether rounded, conical, flat topped

hills with depressions like craters and so forth. Also describe the type of

slopes of the hills, whether steep or gentle or concave or convex. Plateau

high land is recognized if contours on the map observed to show higher

numbers and upland is of the general level dissected by rivers (streams).

State whether the plateaus have hills and they have gentle or steep slope.

Also indicate if the plateaus are of river valleys and other associated

features. Avoid talking about river because these are not relief features,

although it is a physical feature.

Low land relief

Low land relief is recognized if the contours on the map show low numbers of

elevation of the below 500m from the mean sea level and the contours are

widely spaced. Relief of the low land is varied and can be either low land

coastal plains or the low land of the river valley. Low land coastal plain is

recognized by river valleys and when contours on the map is widely spaced

and on the elevation rarely exceed above 300m from the mean sea level.

Beside to this the mapped area is observed to be situated immediately after

the sea. And low land of the river valley is recognized if the contours of the

mapped area are observed to lies parallel to the main river valley for quite

some distance. In low land of the river valley the various features may be

found such as pronounced meanders, ox-bow Lake.

Vegetation interpretation on topographical maps

Vegetation refers to as a community of plants of the distinct species found in

a certain habitant for a particular period of time. Vegetation of a certain area

can be of naturally or artificially occurrence. Natural vegetation are identified

on the area covered on the map if they occupy irregular pattern face and the

artificial one observed by the presence of irregular pattern of appearance.

The common natural vegetation shown include forests, woodland, thicket,

mangrove, shrubs, scrubs, bamboo, riverine, swampy vegetation and

scattered trees. The interpretation of the vegetation on the topographical

maps is done by using a key through it; study the area covered on the map

carefully and identifies various types of the vegetation on the mapped area.

Also natural vegetation on the contour maps can be interpreted or described

according to the following climatic regions:-

i. Equatorial rain forests which characterized by heavy rainfall and high

temperature. These kinds of the natural vegetation are evidencelly

shown on the topographical maps due to the presence of dense or

thick forest of thick trees, epiphytes which grow on trunks of the major

trees. The forest lies 00−50 north and south of the equator and receives

heavy rainfall of about 2000mm annually.

ii. Dedious forests which characterized with little rainfall of about 250mm

throughout the year. These forests are shrubs like which found mainly

in semi desert areas. The forests shed leaves and have well developed

roots system in order to adapt doughtiness of the area. Good example

of the Dedious forest is Acacia trees.

iii. Tropical savannah forests that characterized with moderate rainfall of

about 1500mm throughout the year. The forest lies between latitude

60─200North and South Pole of the equator. On topographical map

tropical savannah forest is evidencelly shown by the presence of

scattered trees and glass land vegetation.

iv. Desert vegetation which characterized with little amount of rainfall of

about 250mm to 500mm throughout the year. On the topographical

maps semi- desert vegetation are evidencelly shown by the presence

of leafless evergreen plants like cacti, aloes and evergreen hard leaf

plant like Europhobia, salt tolerant plants like salt bush (trees).

v. Mountainous forests are shown on the topographical maps due to the

presence of species of trees on high latitudes. Mountainous vegetation

are not uniform all over the mountain due to the effects of temperature

and moisture variation; hence vegetation like rainforest, bamboo

forest, temperature forest and heath and moorland like tussock,

grasses, tough shrubs and short flowering alpine can be seen.

Generally, vegetation cover in a certain area avies accordingly due to the

following reasons:-

Climate of an area

The amount of rainfall and temperature of an area influences the distribution

of vegetation type. For example, the area that receives heavy rainfall and

high well temperature area mostly covered by thick forests and bamboo

vegetation. While the area with moderate rainfall and temperature is

experienced to have scrubs and scattered trees. And there is no vegetation

cover in desert region due to the existence of extreme temperature and lack

of moisture.

Relief and soils

Relief and soil influence the spatial distribution of vegetations over the world.

For example the area with steep slope usually cannot be covered by

vegetation due to the thin, infertile soil available that cannot support plants

growth. On other hand, gentle slopes are covered by different types of

vegetation because of deep and well fertile soil exists that can support the

plants growth. Also very high altitudes experience very low temperature

inhibiting plant growth, thus there is no thick forest at very high altitudes.

The area covered by the volcanic or lime stone rocks may have no

vegetation because the soils in these areas are highly shallow or porous that

cannot support the proper growth of the plants respectively.

Man’s influences

Some parts on the earth’s surface may not have covered by the vegetation

as a result of man’s activities. These vegetations may have been cleared to

give a room for cultivation and settlement. Therefore, on the map look for

evidences such as presence of large plantations or dense settlement to

support the idea that vegetation have been cleared. On other areas on the

earth’s surface can be covered by the forest or vegetation as a result of man

influence through afforestation and reforestation. These are evidencelly

shown on the map by the presence of environmental offices like roots and

shoots office, TANAPA offices, Tacare offices, reserved offices and so forth.

Water bodies

Areas along river valleys have riverine vegetation because the water table is

close to the surface. Also swamps have vegetation due to the availability of

water and this is evidencelly shown on the map to due to the presence of

swampy vegetations. Again, if mangrove found in the area along the shores

of the coast lines indicates the presence of mangrove trees.

Sample of questions:

1. Account for the nature and distribution of vegetation on the map

Mode of the answer

Define vegetation and its distribution and other simple

explanations relating to the nature and the distribution of

vegetation.

With evidence provide the nature of vegetation distribution and

factor influencing their distribution

Recall that, when you are accounting for the distribution of

vegetation or anything else use phrases such as at the region to

the east of the area covered on the map there is ------------, give

reason of its presence

Give the conclusion

2. Explain why vegetations are found on a map

Mode of the answer

Define vegetation and other simple explanations relating to

vegetations.

Give vivid reasons for their presence on the map such as climate,

water bodies, man’s influences and so forth.

Give the conclusion

Drainage and Drainage Pattern Interpretation on Topographical Maps

Drainage is the removal of surface water towards the system of rivers, lakes,

swamps, oceans and other related drainage systems. This removal of

surface water is done through using pipe lines, canals, water pumps, and

other alternative. In the describing of the drainage system of an area

covered on the map one should base on following hints:-

a) State whether the area is well drained or poorly drained. A well-

drained area has many permanent streams and lakes and no swamps

available. While a poorly drained area has extensive seasonal and

permanent swamps, seasonal rivers or extremely few rivers and may

lack any surface drainage.

a) Identify the main river, if any, describe its general direction of flow.

Also describe the general direction of the many rivers and their

distributaries.

b) State if the area has drainage basins with water sheds. Also state

whether the rivers have short courses or whether they disappearance

underground.

c) State whether there are artificial drainage features such as dams,

ponds, waterholes, canals, ditches, aqueducts, manmade lakes and so

forth.

Drainage patterns

This is a layout of plain made by a river system with its tributaries and

distributaries on a landscape. The drainage patterns consider the

arrangement of streams and its tributaries in catchment areas. The pattern

of rivers and other water systems in many areas is the result of some

determinant factors including land slope, difference in hardness of the rocks,

general relief of the area, and climate of the area. The most common

drainage patterns shown on the topographical maps with the reflection to

area represented include Dendritic, Trellis. Radial, Rectangular, Centripetal

and

Dendritic drainage pattern

Dendritic drainage is the one which consists of a network of channels

resembling tree branching. It develops on gently sloping surfaces composed

of materials that respond more or less homogeneously to erosion, such as

areas underlain by nearly horizontal sedimentary rocks. In dendritic

drainage, tributaries join larger channels at various angles but always of less

than 900.

Figure .A dendritic drainage pattern

Radial drainage pattern

Radial drainage pattern is arrangements of stream courses in which the

steams radiate (flow) outwards in all directions from a central zone such as

high volcano. In this drainage pattern all tributaries diverge outwards and

flow from the summit of a rounded high land to the different directions. It

forms a shape of spoke rounded a wheel like structure and it is common to

the area of roughly circular hills of igneous rocks. On the topographical maps

radial drainage pattern is examined easily when different streams move

rounded hills or mountains.

Figure A radial drainage pattern

Centripetal drainage pattern

The centripetal drainage patterns are the stream courses that tend to flow

from different directions and converging at a center of down wrapped

landscape. In the centripetal drainage pattern all streams are moved and

collected into the depression to form a lake or the big river for example, the

depression of Lake Victoria that collect different streams from different

directions of Tanzania and Uganda. Therefore, on the topographical maps

centripetal drainage pattern is examined by the presence of the river steams

that are collected into the depression or other big river stream for example,

river Ruaha, river Ruvu in Tanzania that collect different streams from

different directions of the Tanzania.

Figure .A centripetal drainage pattern

Trellis drainage pattern

Trellis drainage consisting of a network of nearly parallel main streams with

tributaries joining them at nearly right angles. Trellis drainage develops in a

region which is made up of alternate belts of hard and soft rocks which all

dip in the same direction, and which lie at almost right angles to the general

slope down which the consequent stream flows. Erosion of folded

sedimentary rocks developed a landscape of alternating ridges on

resistant rocks and valleys underlain by easily eroded rocks. The tributaries

extend their valleys by head ward erosion into the weak rocks which are

turned into wide valleys, whilst the hard rocks stand up as escarpments. The

tributaries which cut out the valleys, and which do not flow down the main

stream, are called subsequent rivers. This pattern develops in scarp land

regions and regions of folded sedimentary rocks.

Figure A trellis drainage pattern

Fault guided (Rectangular) drainage pattern

This drainage pattern occurs when the tributaries converging to the main

stream at right angle and it tends to have an individual stream taking the

shape like angular bending along it course. The drainage takes the

similarities to the trellised drainage pattern and occurs in the area with the

faulting igneous rocks or it is controlled by geological joint system that

intersect at right angles. It is sometimes called Rectangular drainage

pattern.

Figure .A

faulted guided drainage pattern

Annular drainage pattern

This drainage pattern occurs when the main streams and tributaries are

arranged in a series of the curves around the depression. Tributaries join the

main streams at sharp angles, example Lake Basumtwi in Ghana.

Figure

Parallel drainage pattern

This drainage occurs when the main rivers and tributaries flow parallel to

each other and it forms mainly on the escarpments, dis slopes and ridges.

The drainage pattern is common on slopes that dip towards the same

direction and exists side by side with dendritic drainage pattern.

Fig

ure

Climate Interpretation on Topographical MapsClimate is the average weather condition experienced in an area throughout

the year and normally recorded over thirty years. Climate has a good

number of elements and the most pronounced ones are of rainfall and

temperature. Topographical maps show little direct climatic information of

mapped area. With this the following guides should be taken into

consideration for easy interpretation of the climate on mapped area.

Vegetation types

Natural vegetation and artificial vegetation (crops) shown on the map are

good guides to climate interpretation of an area. For example, area covered

by natural vegetations like forests and bamboo suggest high and well

distributed rainfall and high temperature. And the climate of area with these

characteristics is termed as equatorial climate. The presence of wood land

vegetation and thickets indicate moderate rainfall and low high temperature

which implies Tropical savannah. While the presence of scrub vegetations

and scattered (shrubs) indicate low, seasonal and unreliable rainfall and high

temperature especially in day time which implies dry condition or semi-arid

(semi- desert).

And artificial vegetations (crops) as grow well depending on the climatic

condition that favours its growth are more considered to deduce the climatic

condition of an area. Hence the type of the crop covered on topographical

maps indicates the type of the climatic condition found on a mapped area.

For example, the presence of crops like coffee and tea on the map suggests

that the area covered on the map experiences heavy rainfall and low

temperature and the area with these characteristics experiences

mountainous climate. Presence of cashew nuts, sorghum, millets and

sunflower indicate moderate high seasonal rainfall and high temperature

which indicate semi- arid.

Altitude of an area

Altitude is the height of an area from the mean sea level. Altitude has

considerable impacts on the climatic regime of an area. It is therefore, the

consideration of altitude of an area from the map may help to suggest the

likely climatic condition. With respect to this, once you have been given a

topographical map, consider the altitude of a mapped area by reading the

contour heights to observe the area represented on the map if it is low land

or high land. High land areas above 1500metres suggest high Orographic

rainfall and cool temperature and these indicate mountainous climate. While

low land areas especially those near oceans and lakes suggest high

conventional rainfall and high temperature and these indicate tropical

modified climate.

Latitude of an area

Actually the climate on the earth’s surface differs from one latitude to

another which in leads to the formation of the climatic regions like

equatorial, savannah, semi arid and tundra. The latitudes of the mapped

areas are indicated along the map edges and therefore once you have been

given a topographical maps read and the latitudes of the mapped areas to

understand in which geographical position of the area represented is located

whether in tropical, equatorial or arid region. For instance, if the area is

located from or between 0`─5`north and south of the equator, it implies that

the area is located in the Equatorial belt and likely to experience equatorial

climatic conditions such as high rain fall throughout the year with two

maximum peaks and high temperature throughout the year. And if the map

shows the latitude in between 6`-15`north and south of the equator it

implies the area represented on the map is located in Tropical region and

experienced tropical climatic conditions such as moderate rainfall received

annually (there is both wet and dry seasons) and high temperature but not

throughout the year for example temperature goes as high as 32`C during

the hot season but drop to 21`C during the coolest months.

Water bodies

Drainages are very good guides to interpretation of a climate of particular

area. The amount of rainfall received in an area influences the mounts of

water bodies in the area. For instance, the presence of salt lakes, like Lake

Magadi in Uganda, seasonal streams, bore holes and widely spaced streams

suggest low amount of rainfall is received in the area which indicates that

the area is characterized with high evaporation due to high temperature and

low rainfall. And the area with these characteristics is experienced with semi

arid climatic conditions. Presence of high stream density, permanent rivers,

swamps, lakes and oceans indicate that the area receives heavy and reliable

rainfall and area with these properties experiences Equatorial climate.

However it is important to note that rivers may originate from very wet areas

and drain through very dry areas.

Agriculture

The type of cultivation and animal keeping found in a certain area give the

suggestions on climate of the area. For example, in the areas where

irrigation is carried out suggests low and unreliable rainfall (seasonal

rainfall), such area experiences high temperature causes high evaporation

rates and low humidity rate. This kind of the area with these characteristics

experiences semi- arid climate.

Also animal rearing gives clues on the type of the climate of an area. For

example dairy farming suggests cool temperature and high temperature

which implies mountainous climate. The presence of the ranches indicate low

to moderate rainfall and high temperature, however, these characteristics

indicate tropical climate. Also Pastoralism indicates very high temperature

throughout the year and low, seasonal and unreliable rainfall and this kind of

area involves these characteristics experiences semi arid climate.

Revision exercise 1.1

1. Study the maps extracted from KOROGWE sheet192/2 provided, and

then answer the questions that follows:-

d) State any four ways used to depict relief features on the map?

e) A taxi driver was moving from grid reference 340 328 t0 a filling

station at grid reference 421 305, find the ground distance covered by

a taxi driver in kilometers

f) Convert the linear scale given on the map into statement scale.

g) Identify the main features obtained in the following grid references;-

a. 420 227

b. 350 367

c. 409 345

h) Calculate the area covered by the forest in kilometer squares.

i) Briefly explain any three relief features encourage tourism activities in

the mapped area

j) Draw cross section to show the relief feature of the area mapped from

the grid reference 442 331 to 390 355

2. Study the map extracted from Lindi sheet Y742 and then answer the

questions that follows;-

a. Calculate the area covered by forest in mile squares

b. Convert the linear scale given in representative fraction scale

c. Briefly explain any four major economic activities that exist on a

mapped area.

d. With evidences suggest the type of climate that Lindi found

e. Comment on drainage pattern found on area covered on the map.

Rock description and Geomorphologic process on topographical map

Rocks are aggregates of minerals in solid form that form the earth’s crust

giving it a solid nature. These rocks differ from each other in colour, texture,

density, mode of formation and ability to resist erosion. Rocks like igneous,

sedimentary, and metamorphic are extremely varied and popular. The

surface of the rocks of an area are not directly shown on the map but can be

described by taking the following hints into consideration;-

Nature of the land forms

The nature of the land forms are good guides to surface rocks types

identification of an area covered on the map. For example the presence of

volcanic land forms on the area covered on the map like radiating craters,

caldera, springs, conical hills, geysers reveals the existence of igneous rocks.

And the presence of depressions, sand dunes, mud flow, flood plain,

beaches, coral reef and converging storms on the mapped area indicate the

existence of the sedimentary rocks. Trellis drainage is usually evidence of

folding where parallel out-crops of erodible rocks form valleys between more

resistant ridges, as in the Ridge and Valley region of the Appalachians and

this suggest the existence of sedimentary rocks.

Drainage system

The drainage system in any area strongly relates to the nature of geology of

that area. It thus the consideration of a drainage system may help to suggest

the types of rocks in a particular area. For example the presence of drainage

pattern like parallel, radial on a mapped area reveals the existence of the

igneous rocks simply because the rocks develop in the area with uniform

rock structure(igneous rocks), while the presence of mud flats and marshes

indicate the existence of sedimentary rocks. And if the area covered on the

map is experienced with trellised and rectangular drainage pattern it seems

that the area is covered with sedimentary rocks due to fact that these

patterns develop in the area with soft and hard rock structure. The presence

of many streams on the area covered on the map indicates the existence of

the igneous rocks because these rocks are impermeable and do not allow

water to sink down the ground and the presence of no surface water

streams, and the presence of swamps suggest the existence of the

permeable and easily eroded rocks such as limestone rocks. Also the

presence of internal or interior drainage (drainage which has no outlet and

so does not reach the sea) indicates the presence of soft and hard rock rocks

named as sedimentary rocks that allow surface water to percolate.

Rock permeability

The permeability of the rocks indicates the existence of a certain type of rock

in a certain area. This is due to fact that some rocks allow water to

percolates under groundling while others resist. Topographical maps can

provide identifiable features that suggest the nature of underlying rocks as

follows;-

In humid area permeable rocks show little evidence of surface water in

such a way that the permeability could be a result of rock with high

porosity either due to the present of sand stone or due to high

solubility of rocks such as limestone or due to system of joints.

Therefore, in humid climate where there are permeable rocks

(sedimentary rocks) mapped area will show dry landscape with few

steams.

A line of spring indicates generally the junction of permeable and

impermeable rocks such that surface water percolates in joints or

fissures and emerges on the surface were impermeable out crop. The

region experienced with a line of spring comprises sedimentary and

igneous rocks

Impermeable rocks do not allow free passage of water and where

there are impermeable rocks outcrop on the surface streams are

everywhere and the landscape is marshy and badly drained.

And when impermeable rock outcrop below the permeable strata,

bring the water table to the surface and springs appear on the

mapped area.

Generally the rocks are impermeable and form a variety of landforms.

Suggestive names on map such as ‘’granite quarry’’ or slate quarry,

may help to recognize kind of rocks as igneous or sedimentary rocks

respectively.

Nature of the landscape

The soft rocks are highly eroded compared to the hard one when the

erosional factors (agents) like rainfall, ice and wind operate on the bared

land surface. For example the presence of the highlands, steep slopes

indicate that the rocks are hard and resistances to erosion which are

generally indicate igneous rocks such as granites, and gabbro. And the

presence of low lands, gentle slopes suggest that the rocks are soft and

easily eroded which is generally indicates sedimentary rock such as clay and

shale. Therefore, the nature of the landscape depicts the type of rocks due to

their rock resistance variation against rock erosion.

Vegetation cover

Vegetation is the term that describes the plant species that grow in a

particular area. They usually vary from the place to place due to different

geographical conditions such as soil that derived from the rocks, water

availability, temperature and so forth. For example, the presence of the poor

vegetation cover like scrubs on the area covered on the map indicates the

presence of the sedimentary rocks. This is due to fact that the rocks like lime

stone do not hold water (moisture) to support the growth of plants. And the

area covered by volcano is experienced by the presence of no vegetations

cover because the soil derived from these rocks is highly poor that cannot

support the growth of vegetation.

Human activities

Different human economic activities are conducted depending on the nature

of the rocks available. For example the economic activities like quarrying is

conducted in the area experienced with igneous rocks while the presence of

soft mining like salt mining, and cement mining on the mapped area

suggests the presence of sedimentary rock. Geomorphologic processes are

those Earth’s movements or acts which lead to formation of various land

forms. These land forms can be influenced by the volcanicity, erosion, and

deposition, folding, or faulting and weathering. The identification of

geomorphologic processes on the area covered on the topographical map

suggested by taking into the consideration of the following:-

Land forms

The presence of the land forms on the area covered on the map suggests a

certain kind of the geomorphologic processes that exist on a particular area

either internally or externally of the earth. For example the presence of the

volcanic land forms like crater, caldera, volcanic mountains imply the

presence of volcanicity while the of block mountains, escarpment and

plateau suggest faulting process. And the presence of the mountains which

varies in ranges indicates the presence of folding process. The presence of

the basins suggests the presence of down warping force.

TRANSPORT AND COMMUNICATION INTERPRETATION ON

THE MAP

Transport is the transferring of goods and services from one place to another

while communication is the transforming of the information from one point to

another or from one person to another. In describing the distribution of

transport and communication on a mapped area, study the area covered by

the map carefully and identifies or interprets all the different types of

transport and communication networks like roads, railways, air ways,

pipelines, canals and so forth. For instance: In transport, the forms of the

transport like land transport, water transport and air transport are identified

and well described by stating whether the region covered on the map has a

good or poor transport networks. It has to be noted that the pattern of the

means of transport like roads, rail ways and air ways on the map are

represented with reflection to the area as follows:-

Roads – these are of varied nature and include all weather road bound

surface on the map is shown by means of the following convectional

--------- All weathered bounds surface

-------------All weather loose surface

----Dry weather road

-------------- Foot path

Railways –shown on the map by the convectional representation

-------------------Railway

Air way-are identified by the presence of the air drome and airport where the

air drome on the mapped area is shown by the convectional representation

------------ Air drome

Water transport on the map is identified by the presence of ports, big lakes

and ferry across the rivers.

In communication: Different facilities like telephone lines, post office, TV

tower and mobile offices shown on the map indicate the presence of

communication

FACTORS FOR LOCATING TRANSPORT AND COMMUNICATIONIt has noted that the pattern of the means of transport and communication

on the map with reflection to the areas represented influenced by the

following factors.

Relief factor affect transport and communication in various ways in a

way that roads and rail lines tend to follow regions of gentle slope and

fairly straight in low lands or plains because of highly floods prone.

Also avoiding steep slopes and meanders.

Drainage system is another factor that influences the construction of

means of transport and communication in a certain area. Roads and

railways are constructed some distance away from river valleys and

swamps to avoid floods. Also rail lines and roads avoid crossing many

river valleys in order to avoid too many expenses for many bridges

constructions

Economic activities also influence the construction of transport and

communication in a certain area simply because the means of

transport and communication are made to pass through the areas with

economic activities like in rich farming zones, mining zone et-cetra.

Residential areas, means of transport and communication are well

spread in the areas with settlements in order to facilitate movements

of the people as well their goods (properties). On the hand, dry band

unsettled areas will have very few means of transport and

communication like roads, telephone lines and post offices.

Revision exercise 1.3

1. Carefully study the map extract of Tabora sheet 118/2 and then

answer the following questions:-

a. Calculate the length of the road from Kigwa grid reference 890 408

to town center grid reference 796 446 in km.

b. Calculate the area covered by swamps in km2

c. With evidences state three major means of transport found in

Tabora.

d. Comment on the economic activities conducted in Tabora region

2. Carefully study the map extract of MUSOMA provided, and then

answers the following questions.

Settlement and Population distribution on the mapSETTLEMENTS are all forms of grouping of human habitations or are the

permanent occupation of site by a group of individuals. Settlements are area

lands exclusively or predominantly used for human settlements which may

be urban, rural or ethnics reserves. Settlements come in lots of different

sizes and shapes. A settlement may be permanent or temporary for example

refugee camps that have been built in conflict zones are temporary

settlements. Human population refers to the group of the people occupying

or the residing in a certain geographical unit. And the population distribution

on the map refers to the way in which people are spread on the map

provided that can be either evenly distributed or uneven distributed.

Therefore, when the teachers and students discuss settlement and spatial

distribution of the population for particular area covered on the map they

must state whether the population is evenly or unevenly distributed by

giving out the concrete reasons for their distribution. There are three

geographical factors that can be used to infer the reasons of development

and functions of a settlements in a certain locations which are;-

a) Site which refer to actual area of land on which settlements stand and

this site can be flat or elevated. Settlement on elevated site above the

flood plain or river may be developed to avoid the danger of floods and

easy access to water supply.

b) Shape that provides a clue of which settlement has grown that may be

nucleated around the market center or linear along the transportation

route.

c) Situation which refers to the relationship with surrounding land and

water features example water seeking settlement. A settlement

developed near a spring may be water seeking settlement

Type of settlementsUrban settlements which develop in town administrative centers

characterized with transportation junctions and highly populated. A good

number of the people approximately to over 80% engaged in non-

agricultural activities.

Rural settlements which develop in villages and the majority of the people

are approximated to be over 50% engaged in agricultural sectors as their

main economic activity. On the most topographical maps, rural settlements

shown by means of the black round dots and the arrangement of houses in

rural settlements are extremely varied.

Pattern of the settlement Settlement pattern is the layout of houses in habitable areas where people

live and conduct their socio- economic activities by interacting with the

prevailing environment. Settlement patterns deal with the physical

arrangement of structures, roads, and other major created landscapes that

reflects cultural values, level of technology, population density and

livelihood. A good number of topographical maps show settlement patterns.

Settlements on topographical map are given by means of selected

convectional symbols. There are four types of the settlement patterns that

can be recognized on the map as linear, nucleated, dispersed and scattered

settlements. Settlements are established on allocation because one location

possesses natural advantages over the surrounding areas. In map

interpretation we try to find evidence from the map the nature of these

advantages and give some reasons why a certain site was chosen rather

than other. Also from the map we can infer the functions of the settlements

and activities of the people in given locations.

Linear Settlement Pattern

This is the settlement created along the infrastructure networks like roads,

railways, and along the coast lines as well as rivers due to their economic

significances.

LINEAR SETTLEMENTS

Nucleated Settlement

This is the settlement in there are many settlements clustered together and

is the pattern is common to areas of communal society, where there is

supply of a certain economic resources and everyone is on need of it, also

relief barriers which make people to concentrate in more less hazardous

areas.

NUCLEATED SETTLEMENT

Dispersed Settlement

This is a rural settlement where people live scattered houses, and also

referred to as scattered settlements. The houses are widely spaced one to

another and it is common in areas of pastoral societies and where individual

forms are large enough and population is too spaced.

SCATTERED SETTLEMENT

Scattered Clustered Settlement

This is the settlement where settlement occurs in clusters dispersed

SCATTERED CLUSTERED SETTLEMENT

Factors encouraging spatial distribution of Settlements on the mapsA reliable source of the water supply Settlements may be sited near source of water such as rivers and fresh

lakes. The water is used for irrigation and industrial purposes. However it is

important to note that the settlements are usually some distance away from

the water sources for fear of the flooding.

Relief factor (topography)The relief of an area influences the settlement pattern of a particular area.

For example most of the people avoid setting settlements on the very steep

area such as on the escarpments and hills. This is because such areas are

hard to work in, inaccessible and are prone to soil erosion and mass wasting.

Gentle slope and plains usually have more settlements because such areas

are easy to work, accessible and poor prone to soil erosion and mass

wasting.

Drainage systemAreas covered by the swamps, regions near lakes and rivers have barely any

settlement because these areas are prone to flooding. Such areas may also

have stagnant, water especially after heavy rainfall which could encourage

breeding of pests. There is also fear or danger of water borne diseases.

Vegetation coverIn the areas covered on the map which are thickly forested have no

settlements, since these areas are difficult to clear and for developing the

settlement patterns. Also some of the forests are governed as reserves;

hence no one is allowed to settle there. Woodlands may also not be settled

in because sometimes they may be infected with tsetse flies which cause

sleeping sickness.

Soil factorDeep and well drained fertile soil attracts dense settlements because it

favors the cultivation of crops. Also some large rivers with a lot of alluvial

deposits may have dense settlements due to cultivation of crops.

Agriculture In the area covered on the map agriculture which is indicated due to the

presence of the large plantations and ranches. These areas usually will have

or no settlements, sparse settlements since they have been preserved for

the growing of a certain crop or for the rearing of livestock. However, there

are may be labor lines on the plantations.

UrbanizationThe urban areas usually attract large numbers of people from the rural

areas. As a result, urban centers are normally having very high concentration

of settlements.

Factors deterring or discouraging spatial distribution of Settlements on the

maps

Marshy or swamps areas

In the topographical maps marshy or swampy areas usually symbols for

seasonal or permanent swampy will be printed on such areas, more

importantly the contours are very wide indicating a flat land in which

settlements are discouraged.

Steep slopesThe steep slope of an area give the difficulties for roads and railways

construction and land erosion and mass wasting are common which

discourage the growing of the crops and the development of the settlements.

Reserved areasReserved areas discourage the settlements by laws known by government

lands and reserved for national parks, game reserve or for future

government planning.

Unpleasant climatic conditionUnpleasant climatic condition example prolonged drought gives the

difficulties to cultivation of the crops and water supply for domestic uses and

other.

Land use In this publication, land-use means the proper use of physical, social and

economic factors in such a way as to assist and increase the productivity, so

as to meet the needs of society. Farmers and other land users can, and

should, take an active part in deciding on how to use land so as to bring

social as well as economic improvement. Through the settlement designs the

land user perform different functions accordingly. Therefore, the settlement

designs on the topographical maps can depict land users’ functions as;

a) Some towns are trading centers which are indicated by the presence of

the stores such as ware houses, roads, converging in the town, shops

and markets.

b) Other towns are administrative centers suggested by the presence of

the chief’s camps, police posts, D.C’s office, D.O’s office, court houses,

military camps etc.

c) They can be educational centers indicated by the presence of the

universities, colleges and schools

d) They can be transport and communication suggested by the presence

of the means of the transport and communication like roads, railways,

air ports, harbours, telephone lines, post offices, bus stands.

e) They can be health centers indicated by the presence of hospitals and

dispensaries.

f) They can be industrial centers indicated by the presence of the

factories and industrial plants.

g) Some towns are agricultural centers evidenced by the presence of the

stores, creameries, dairies, silos, depots etc. such towns collect and

distribute agricultural products.

h) They can be mining centers suggested by the presence of the quarries,

mineral work, mines etc.

i) They may be religious centers evidenced by the presence of the

churches, mosques and temples

j) They may be recreational and sports center indicated by the presence

of the gardens, cinema halls, stadium and golf courses.

k) Towns may be cultural centers indicated by the presence of the

theatres.

Sample of the questions Analysis of the land use pattern on the map

Briefly explain the functions of town X

INTERPRETATION OF HUMAN ACTIVITIES ON THE MAPSWhen the teachers and the students interpret the human activities on the

map, they must consider the kind of the activity which can be either social or

economic demand. These social activities including education, medical care,

security services, entertainments and others provided so as to meet the

need of society in order to ensure social development. And economic

activities are those tasks conducted for income earning to improve economic

growth of an individual or society as whole such as mining and quarrying,

agriculture, lumbering, irrigation, fishing and trading.

Social activities on the topographical maps can be identified as;-

a) Education that is identified due to the presence of the social

services like schools, colleges and universities, or any

educational centers.

b) Health care is identified by the presence of the hospitals and

dispensaries or any health center.

c) Security which is indicated by the presence of the police

station or post, military camps, prison and so forth.

d) Entertainment is indicated by the presence of the clubs, rent

houses, hotels, models and so forth.

e) Worship is identified by the presence of the temples,

mosques, mission centers and churches.

Economic activities on the topographical maps can be identified as:-

Agriculture activity

On the topographical maps agriculture activity is sub divided into the crop

farming and livestock farming as described below;-

CROP FARMING

Plantation (large scale) farming which is for commercial purposes is

suggested by the presence of the green diagonals lines that are drawn on

the map extracted. These diagonal lines refer to the key to find out the type

of the crops grown and the crops grown on plantations include tea, coffee,

sisal, sugar cane, cotton, and wattle among others.

Small scale cash crop growing is evidenced by the presence of the tea, and

coffee factories for processing, cotton ginneries, sugar juggleries, market

and so forth. Subsistence farming which is indicated by the presence of

dense rural settlement also may be suggested on the topographical maps.

Irrigation activitiesOn the topographical maps irrigation activity as one of the economic

activities is suggested when farming activities conducted along the water

bodies. Irrigation activity is possible to grow crops like fruits, vegetables,

rice, maize, and banana trees. It is difficult to irrigate crops like baobab,

coconut and other crops of the same kind.

LIVESTOCK FARMING

Commercially livestock farming is indicated by the presence of the

veterinary offices, creameries, dairies, meat processing plants, cattle dips

and ranches.

Pastoralism is also indicated on the topographical maps by the presence of

the grass land vegetation, scattered clusters of settlements, water holes,

bore holes dams, water pumps, quarantine camps and cattle dips.

MINING AND QUARRYING

This is an extraction of minerals from their ores like salts, magadi soda,

diamond, gold and so forth. On a map mining and quarrying is evidenced by

the presence of lakes in dry rift valley floor which shows the exploitation of

the minerals like salt or magadi soda, presence of the power supply in a

nucleated settlement, gravels quarries, a lot of water setlines, resting and so

forth.

LUMBERING ACTIVITY

This is the extraction of wood products from the trees, and on the map this is

indicated by the presence of forests, forest guard posts and dressing plants

appearing on a map for the process of extracting timbers (wood). However,

some forests are reserved and therefore no lumbering may be allowed. It is

therefore important to cite evidence on the map before concluding that there

is lumbering in an area.

FISHING ACTIVITY

Fishing activity refers to the extraction of the fish species from water bodies

like oceans, rivers, lakes, seas, swamps. The fishing activity is evidenced

shown by the presence of the dense settlement along the shores of lakes or

oceans or big rivers, together with fish traps, ponds, fish fillet factories,

fishing cooperatives, fishing farms, fish hatcheries, fishing department and

so forth.

TRADING ACTIVITY

The exchange of goods and services by selling and buying them are

suggested by the presence of the a wide variety of economic activities,

dense road network, presence of railway lines, airports, ocean or lake ports,

presence of towns, markets and shops. The presence of population in an

area itself, just indicates the presence of trading activity due to fact that

people engage into the exchange of goods and services (trading) in order to

meet their daily lives.

MANUFACTURING AND PROCESSING ACTIVITY

On the maps the process of processing and changing the raw materials into

finished goods of high value to human is indicated the presence of industries

and factories (installations). The presence of activities like ginning, hulling,

crops processing such as tea and coffee, brick making, quarrying, salt works

and so forth also suggest the presence of manufacturing and processing

activities (industries)

TOURISM ACTIVITY

The movement of the people internally or externally of the countries for

purposes of studying, research, or leisure is depicted on the topographical

maps by the presence of the camping sites, national parks, picnic sites,

tourisms resort centers, pre- historical sites and among others.

TRANSPORT AND COMMUNICATION ACTIVITY

On the maps transport and communication is suggested by the presence of

network of roads, railways, air way, sea ports (harbours) and the presence of

telephone lines, telecom offices, pipe lines, and post offices and so on.

Transportation on the topographical maps can be classified as land

transportation when transportation networks like roads, and railways are

depicted and air transportation when air ports and sometimes doldrums are

indicated on the topographical maps. Also, when the water bodies like lakes,

oceans or seas are shown on the topographical maps indicate water

transportation called navigation.

Exercise revision 1.4

CHAPTER 03PHOTOGRAPH READING AND INTERPRETATION

SPECIFIC OBJECTIVE: BY THE END OF THIS TOPIC, EVERY STUDENT SHOULD BE ABLE TO:-

i. Identify correct types of photograph without teacher’s help

ii. Differentiate between ground, oblique photographs and

vertical without teacher’s assistance

iii. Read correct features presented on photographs without

teacher’s help

iv. Identify natural and manmade features in the fore, middle and

back ground of the photograph without teacher’s assistance

v. Interpret features presented on the photograph without

teacher’s assistance

Chapter 04

APPLICATION OF STATISTICS IN GEOGRAPHY

Specific Objectives: By the end of this topic, each student should be able to:-

i. Explain the concept of statistics without teacher’s assistance

correctly

ii. Differentiate types of statistical data without teacher’s help

iii. Present data graphically without teacher’s assistance correctly

iv. Explain the importance of statistics to the statistics user on

his/her own words correctly.

v. Describe how massive data can be summarized without

teacher’s help

vi. Describe methods of presenting simple and complex(mixed)

data without teacher’s help

vii. Calculate the mean, median and mode of statistical data

without teacher’s guide correctly.

viii. Explain the significant of mean. Median and mode without

teacher’s help correctly.

ix. Interpret the data using simple statistical measures without

teacher’s assistance

Meaning of Statistics:

Statistics is concerned with scientific methods for collecting, organising,

summarising, presenting and analysing data as well as deriving valid conclusions

and making reasonable decisions on the basis of this analysis. Statistics is

concerned with the systematic collection of numerical data and its interpretation.

The word ‘statistic’ is used to refer to Numerical facts, such as the number of

people living in particular area or the study of ways of collecting, analysing and

interpreting the facts. Statistics is only, one of the methods of studying a

problem: Statistical method do not provide complete solution of the problems

because problems are to be studied taking the background of the countries

culture, philosophy or religion into consideration. Thus the statistical study

should be supplemented by other evidences. It does not study individuals

because it does not give any specific importance to the individual items, in fact it

deals with an aggregate of objects. Individual items, when they are taken

individually do not constitute any statistical data and do not serve any purpose

for any statistical enquiry.

Functions of Statistics:

There are many functions of statistics. Let us consider the following five

important functions.

i. Condensation: Generally speaking by the word ‘to condense’, we mean to

reduce or to lessen. Condensation is mainly applied at embracing the

understanding of a huge mass of data by providing only few observations.

If in a particular class in Chennai School, only marks in an examination are

given, no purpose will be served. Instead if we are given the average mark

in that particular examination, definitely it serves the better purpose.

Similarly the range of marks is also another measure of the data. Thus,

Statistical measures help to reduce the complexity of the data and

consequently to understand any huge mass of data.

ii. Comparison: Classification and tabulation are the two methods that are

used to condense the data. They help us to compare data collected from

different sources. Grand totals, measures of central tendency measures of

dispersion, graphs and diagrams, coefficient of correlation etc provide

ample scope for comparison. If we have one group of data, we can compare

within itself. If the rice production (in Tonnes) in Tanjore district is known,

then we can compare one region with another region within the district. Or

if the rice production (in Tonnes) of two different districts within Tamilnadu

is known, then also a comparative study can be made. As statistics is an

aggregate of facts and figures, comparison is always possible and in fact

comparison helps us to understand the data in a better way.

iii. Forecasting: By the word forecasting, we mean to predict or to estimate

beforehand. Given the data of the last ten years connected to rainfall of a

particular district in Tamilnadu, it is possible to predict or forecast the

rainfall for the near future. In business also forecasting plays a dominant

role in connection with production, sales, profits etc. The analysis of time

series and regression analysis plays an important role in forecasting.

iv. Estimation: One of the main objectives of statistics is drawn inference

about a population from the analysis for the sample drawn from that

population. The four major branches of statistical inference are

a) Estimation theory

b) Tests of Hypothesis

c) Non Parametric tests

d) Sequential analysis

Estimation theory: In estimation theory, we estimate the unknown value of the

population parameter based on the sample observations. Suppose we are given a

sample of heights of hundred students in a school, based upon the heights of

these 100 students, it is possible to estimate the average height of all students in

that school.

Tests of Hypothesis: A statistical hypothesis is some statement about the

probability distribution, characterizing a population on the basis of the

information available from the sample observations. In the formulation and

testing of hypothesis, statistical methods are extremely useful. Whether crop

yield has increased because of the use of new fertilizer or whether the new

medicine is effective in eliminating a particular disease are some examples of

statements of hypothesis and these are tested by proper statistical tools.

Scope of Statistics:

Statistics is not a mere device for collecting numerical data, but as a means of

developing sound techniques for their handling, analysing and drawing valid

inferences from them. Statistics is applied in every sphere of human activity –

social as well as physical – like Biology, Commerce, Education, Planning, Business,

Management, Information Technology, etc. It is almost impossible to find a single

department of human activity where statistics cannot be applied. We now discuss

briefly the applications of statistics in other disciplines.

Statistics and Industry:

Statistics is widely used in many industries. In industries, control charts are

widely used to maintain a certain quality level. In production engineering, to find

whether the product is conforming to specifications or not, statistical tools,

namely inspection plans, control charts, etc., are of extreme importance. In

inspection plans we have to resort to some kind of sampling – a very important

aspect of Statistics.

Statistics and Commerce:

Statistics are lifeblood of successful commerce. Any businessman cannot afford to

either by under stocking or having overstock of his goods. In the beginning he

estimates the demand for his goods and then takes steps to adjust with his

output or purchases. Thus statistics is indispensable in business and commerce.

As so many multinational companies have invaded into our Indian economy, the

size and volume of business is increasing. On one side the stiff competition is

increasing whereas on the other side the tastes are changing and new fashions

are emerging. In this connection, market survey plays an important role to exhibit

the present conditions and to forecast the likely changes in future.

Statistics and Agriculture:

Analysis of variance (ANOVA) is one of the statistical tools developed by Professor

R.A. Fisher, plays a prominent role in agriculture experiments. In tests of

significance based on small samples, it can be shown that statistics is adequate to

test the significant difference between two sample means. In analysis of variance,

we are concerned with the testing of equality of several population means.

For an example, five fertilizers are applied to five plots each of wheat and the

yield of wheat on each of the plots are given. In such a situation, we are

interested in finding out whether the effect of these fertilizers on the yield is

significantly different or not. In other words, whether the samples are drawn from

the same normal population or not. The answer to this problem is provided by the

technique of ANOVA and it is used to test the homogeneity of several population

means.

Statistics and Economics:

Statistical methods are useful in measuring numerical changes in complex groups

and interpreting collective phenomenon. Nowadays the uses of statistics are

abundantly made in any economic study. Both in economic theory and practice,

statistical methods play an important role.

Alfred Marshall said, “Statistics are the straw only which I like every other

economist have to make the bricks”. It may also be noted that statistical data and

techniques of statistical tools are immensely useful in solving many economic

problems such as wages, prices, production, distribution of income and wealth

and so on. Statistical tools like Index numbers, time series Analysis, Estimation

theory, Testing Statistical Hypothesis are extensively used in economics.

Statistics and Education: Statistics is widely used in education. Research has

become a common feature in all branches of activities. Statistics is necessary for

the formulation of policies to start new course, consideration of facilities

available for new courses etc. There are many people engaged in research work

to test the past knowledge and evolve new knowledge. These are possible only

through statistics.

Statistics and Planning: Statistics is indispensable in planning. In the modern

world, which can be termed as the “world of planning”, almost all the

organisations in the government are seeking the help of planning for efficient

working, for the formulation of policy decisions and execution of the same.

In order to achieve the above goals, the statistical data relating to production,

consumption, demand, supply, prices, investments, income expenditure etc and

various advanced statistical techniques for processing, analysing and interpreting

such complex data are of importance. In India statistics play an important role in

planning, commissioning both at the central and state government levels.

Statistics and Medicine: In Medical sciences, statistical tools are widely used. In

order to test the efficiency of a new drug or medicine, t - test is used or to

compare the efficiency of two drugs or two medicines, t-test for the two samples

is used. More and more applications of statistics are at present used in clinical

investigation.

Statistics and Modern applications:

Recent developments in the fields of computer technology and information

technology have enabled statistics to integrate their models and thus make

statistics a part of decision making procedures of many organisations. There are

so many software packages available for solving design of experiments,

forecasting simulation problems etc.

SYSTAT, a software package offers mere scientific and technical graphing options

than any other desktop statistics package. SYSTAT supports all types of scientific

and technical research in various diversified fields as follows

1. Archeology: Evolution of skull dimensions

2. Epidemiology: Tuberculosis

3. Statistics: Theoretical distributions

4. Manufacturing: Quality improvement

5. Medical research: Clinical investigations.

6. Geology: Estimation of Uranium reserves from ground

water

Chapter 05

INTRODUCTION TO RESEARCH

Specific Objectives: By the end of this topic, every

students should be able to:-

i. Explain the meaning of research on his or her own

words correctly.

ii. Assess the importance of research in daily life

without teacher’s help.

iii. Describe the research stages in conducting a

research without teacher’s assistance.

iv. Conduct research in school level without teacher’s

help.

v. Explain the use of research output and

recommendations without teacher’s help.

DEFINITION OF RESEARCH

The word research is composed of two syllables, re and search.

Re is a prefix meaning again, anew or over again and search is a

verb meaning to examine closely and carefully, to test and try, or

to probe. Together they form a noun describing a careful,

systematic, patient study and investigation in some field of

knowledge, undertaken to establish facts or principles. Therefore,

research is a structured enquiry that utilizes acceptable scientific

methodology to solve problems and create new knowledge that is

generally applicable. Scientific methods consist of systematic

observation, classification and interpretation of data. Although we

engage in such process in our daily life, the difference between

our casual day- to-day generalisation and the conclusions usually

recognized as scientific method lies in the degree of formality,

rigorousness, verifiability and general validity of latter.

Key terms:

Research

Research problem

Research topic

Field research

Field work

Field study

Research methods or tools

Research techniques

Objectives of research

Qualities or criteria of good research

CHARACTERISTICS OF GOOD RESEARCH:

Research is a process of collecting, analyzing and interpreting

information to answer questions. But to qualify as research, the

process must have certain characteristics: it must, as far as

possible, be controlled, rigorous, systematic, valid and verifiable,

empirical and critical.

a) Good research is Controlled- in real life there are many

factors that affect an outcome. The concept of control

implies that, in exploring causality in relation to two

variables (factors), you set up your study in a way that

minimizes the effects of other factors affecting the

relationship. This can be achieved to a large extent in the

physical sciences (cookery, bakery), as most of the research

is done in a laboratory. However, in the social sciences

(Hospitality and Tourism) it is extremely difficult as research

is carried out on issues related to human beings living in

society, where such controls are not possible. Therefore in

Hospitality and Tourism, as you cannot control external

factors, you attempt to quantify their impact.

b) Good research is rigorous-you must be scrupulous in

ensuring that the procedures followed to find answers to

questions are relevant, appropriate and justified. Again, the

degree of rigor varies markedly between the physical and

social sciences and within the social sciences.

c) Good research is systematic-this implies that the procedure

adopted to undertake an investigation follow a certain logical

sequence. The different steps cannot be taken in a

haphazard way. Some procedures must follow others.

d) Good research is Valid and verifiable-this concept implies

that whatever you conclude on the basis of your findings is

correct and can be verified by you and others.

e) Good research is empirical-this means that any conclusion

drawn is based upon hard evidence gathered from

information collected from real life experiences or

observations.

f) Good research is Critical-critical scrutiny of the procedures

used and the method employed is crucial to a research

enquiry. The process of investigation must be foolproof and

free from drawbacks. The process adopted and the

procedures used must be able to withstand critical scrutiny.

g) Good research is logical: This implies that research is guided by the rules of logical reasoning and the logical process of induction and deduction are of great value in carrying out research. Induction is the process of reasoning from a part to the whole whereas deduction is the process of reasoning from some premise to a conclusion which follows from that very premise. In fact, logical reasoning makes research more meaningful in the context of decision making.

h) Good research is replicable: This characteristic allows research results to be verified by replicating the study and thereby building a sound basis for decisions.

For a process to be called research, it is imperative that it has the

above characteristics.

CRITERIA or QUALITIES OF GOOD RESEARCHWhatever may be the types of research works and studies, one thing that is important is that they all meet on the common ground of scientific method employed by them. One expects scientific research to satisfy the following criteria:1. The purpose of the research should be clearly defined and common concepts be used.2. The research procedure used should be described in sufficient detail to permit another researcher to repeat the research for further advancement, keeping the continuity of what has already been attained.3. The procedural design of the research should be carefully planned to yield results that are as objective as possible.4. The researcher should report with complete frankness, flaws in procedural design and estimate their effects upon the findings.5. The analysis of data should be sufficiently adequate to reveal its significance and the methods of analysis used should be appropriate. The validity and reliability of the data should be checked carefully.6. Conclusions should be confined to those justified by the data of the research and limited to those for which the data provide an adequate basis.7. Greater confidence in research is warranted if the researcher is experienced, has a good reputation in research and is a person of integrity.

TYPES OF RESEARCH

Research can be classified from three perspectives:

1. Basing on Application of research study

2. Objectives in undertaking the research

3. Inquiry mode employed

1. Application:

From the point of view of application, there are two broad

categories of research:

a) Pure research which involves developing and testing

theories and hypotheses that are intellectually challenging

to the researcher but may or may not have practical

application at the present time or in the future. The

knowledge produced through pure research is sought in

order to add to the existing body of research methods.

b) Applied research is done to solve specific, practical

questions; for policy formulation, administration and

understanding of a phenomenon. It can be exploratory, but

is usually descriptive. It is almost always done on the basis

of basic research. Applied research can be carried out by

academic or industrial institutions. Often, an academic

institution such as a university will have a specific applied

research program funded by an industrial partner interested

in that program.

2. Objectives:

From the point of view objectives, a research can be classified as

a) Descriptive research that includes surveys and fact-finding

enquiries of different kinds. The major purpose of descriptive

research is description of the state of affairs as problem,

phenomenon, service or programme, or provides information

about , say, living condition of a community, or describes

attitudes towards an issue as it exists at present. The main

characteristic of this method is that the researcher has no

control over the variables; he can only report what has

happened or what is happening.

b) Correlational research attempts to discover or establish the

existence of a relationship/ interdependence between two or

more aspects of a situation.

c) Explanatory research attempts to clarify why and how there

is a relationship between two or more aspects of a situation

or phenomenon.

d) Exploratory research is undertaken to explore an area where

little is known or to investigate the possibilities of

undertaking a particular research study (feasibility study /

pilot study). In practice most studies are a combination of

the first three categories.

3. Inquiry Mode:

From the process adopted to find answer to research questions –

the two approaches are:

a) Structured approach:

The structured approach to inquiry is usually classified as

quantitative research. Here everything that forms the research

process- objectives, design, sample, and the questions that you

plan to ask of respondents- is predetermined. It is more

appropriate to determine the extent of a problem, issue or

phenomenon by quantifying the variation. e.g. how many people

have a particular problem? How many people hold a particular

attitude?

b) Unstructured approach:

The unstructured approach to inquiry is usually classified as

qualitative research. This approach allows flexibility in all aspects

of the research process. It is more appropriate to explore the

nature of a problem, issue or phenomenon without quantifying it.

Main objective is to describe the variation in a phenomenon,

situation or attitude. E.g. description of an observed situation, the

historical enumeration of events, an account of different opinions

different people have about an issue, description of working

condition in a particular industry.

Both approaches have their place in research. Both have their

strengths and weaknesses.

In many studies you have to combine both qualitative and

quantitative approaches. For example, suppose you have to find

the types of cuisine / accommodation available in a city and the

extent of their popularity.

Types of cuisine are the qualitative aspect of the study as finding

out about them entails description of the culture and cuisine. The

extent of their popularity is the quantitative aspect as it involves

estimating the number of people who visit restaurant serving

such cuisine and calculating the other indicators that reflect the

extent of popularity.

THE RESEARCH PROCESS

The research process is similar to undertaking a journey. For a

research journey there are two important decisions to make-

1) What you want to find out about or what research questions

(problems) you want to find answers to;

2) How to go about finding their answers.

There are practical steps through which you must pass in your

research journey in order to find answers to your research

questions. The path to finding answers to your research questions

constitutes research methodology. At each operational step in the

research process you are required to choose from a multiplicity of

methods, procedures and models of research methodology which

will help you to best achieve your objectives. This is where your

knowledge base of research methodology plays a crucial role.

Steps in Research Process are as follows:-

1. Formulating the Research Problem

2. Extensive Literature Review

3. Hypothesis formulation

4. Preparing the Research Design including Sample Design

5. Collecting the Data

6. Analysis of Data

7. Generalization and Interpretation

8. Preparation of the Report or Presentation of Results-Formal

write ups of conclusions reached.

Step1. Formulating the research problem:

It is the first and most crucial step in the research process and the

main function is to decide what you want to find out about. The

way you formulate a problem determines almost every step that

follows.

1. Study population-They provide you with the information or

you collect information about them. People: individuals,

organizations, groups, communities

2. Subject area-Information that you need to collect to find

answers to your research questions. You can examine the

professional field of your choice in the context of the four Ps in

order to identify anything that looks interesting.

Considerations in selecting a research problem:

These help to ensure that your study will remain manageable and

that you will remain motivated.

1. Interest: a research endeavour is usually time consuming, and

involves hard work and possibly unforeseen problems. One should

select topic of great interest to sustain the required motivation.

2. Magnitude: It is extremely important to select a topic that you

can manage within the time and resources at your disposal.

Narrow the topic down to something manageable, specific and

clear.

3. Measurement of concepts: Make sure that you are clear

about the indicators and measurement of concepts (if used) in

your study.

4. Level of expertise: Make sure that you have adequate level

of expertise for the task you are proposing since you need to do

the work yourself.

5. Relevance: Ensure that your study adds to the existing body

of knowledge, bridges current gaps and is useful in policy

formulation. This will help you to sustain interest in the study.

6. Availability of data: Before finalizing the topic, make sure

that data are available.

7. Ethical issues: How ethical issues can affect the study

population and how ethical problems can be overcome should be

thoroughly examined at the problem formulating stage.

Steps in formulation of a research problem:

Working through these steps presupposes a reasonable level of

knowledge in the broad subject area within which the study is to

be undertaken. Without such knowledge it is difficult to clearly

and adequately ‘dissect’ a subject area.

Step1. Identify a broad field or subject area of interest to you.

2. Dissect the broad area into sub areas.

3. Select what is of most interest to you.

4. Raise research questions.

5. Formulate objectives.

6. Assess your objectives.

7. Double check.

So far we have focused on the basis of your study, the research

problem. But every study in social sciences has a second element,

the study population from whom the required information to find

answers to your research questions is obtained. As you narrow

the research problem, similarly you need to decide very

specifically who constitutes your study population, in order to

select the appropriate respondents.

Step2. Reviewing the literature:

-Essential preliminary task in order to acquaint yourself with the

available body of knowledge in your area of interest.

-Literature review is integral part of entire research process and

makes valuable contribution to every operational step.

-Reviewing literature can be time-consuming, daunting and

frustrating, but is also rewarding. Its functions are:

a. Bring clarity and focus to your research problem;

The process of reviewing the literature helps you to understand

the subject area better and thus helps you to conceptualise your

research problem clearly and precisely. It also helps you to

understand the relationship between your research problem and

the body of knowledge in the area.

b. Improve your methodology:

A literature review tells you if others have used procedures and

methods similar to the ones that you are proposing, which

procedures and methods have worked well for them, and what

problems they have faced with them. Thus you will be better

positioned to select a methodology that is capable of providing

valid answer to your research questions.

c. Broaden your knowledge base in your research area:

It ensures you to read widely around the subject area in which

you intend to conduct your research study. As you are expected

to be an expert in your area of study, it helps fulfill this

expectation. It also helps you to understand how the findings of

your study fit into the existing body of knowledge.

d. Contextualize your findings:

How do answers to your research questions compare with what

others have found? What contribution have you been able to

make in to the existing body of knowledge? How are your findings

different from those of others? For you to be able to answer these

questions, you need to go back to your literature review. It is

important to place your findings in the context of what is already

known in your field of enquiry. Procedure for reviewing the

literature:

i. Search for existing literature:

To effectively search for literature in your field of enquiry, it is

imperative that you have in mind at least some idea of broad

subject area and of the problem you wish to investigate, in order

to set parameters for your search. Next compile a bibliography for

this broad area. Sources are:

1. Books

2. Journals

BOOKS comprise a central part of any bibliography. Advantage-

material published generally is of good quality and the findings

are integrated with other research to form a coherent body of

knowledge. Disadvantage-material is not completely up to date,

as it can take a few years between the completion of a work and

publication in the form of a book. Search for books in your area of

interest, prepare a final list, locate these books in the libraries or

borrow from other sources. Examine their content, if contents are

not found to be relevant to your topic, delete it from your reading

list.

JOURNALS

Journals provide you with the most up-to-date information, even

though there is a gap of two to three years between the

completion of a research project and the publication in a journal.

As with books, you need to prepare a list of journals for identifying

literature relevant to your study. This can be done as follows:

-locate the hard copies of the journal that are appropriate to your

study;

- use the internet

- look at the index of research abstracts in the relevant field to

identify and read the articles. Whichever method you choose, first

identify the journals you want to look at in more detail for your

review of literature. Select the latest issue; examine its content

page to see if there is an article of relevance to your research

topic. If you feel a particular article is of relevance to you, read its

abstract. If you think you are likely to use it, photocopy or prepare

a summary and record it for reference for later use.

ii. Review the literature selected:

After identifying books and articles as useful, the next step is to

start reading them critically to pull together themes and issues

that are associated. If you do not have a theoretical framework of

themes in mind to start with, use separate sheets of paper for

each article or book. Once you develop a rough framework, slot

the findings from the material so far reviewed into that

framework, using a separate sheet of paper for each theme of

that framework. As you read further, go on slotting the

information where it logically belongs under the theme so far

developed. You may need to add more themes as you go. Read

critically with particular reference to the following aspects:

• Note whether the knowledge relevant to your theoretical

framework is confirmed beyond doubt.

• Note the theories put forward, the criticisms of these and their

basis, the methodologies adopted and the criticisms of them.

• Examine to what extent the findings can be generalized to other

situations.

Ascertain the areas in which little or nothing is known-the gaps

that exist in the body of knowledge.

iii. Develop a theoretical framework:

As you have limited time it is important to set parameters by

reviewing the literature in relation to some main themes pertinent

to your research topic. As you start reading the literature, you will

realize that it deals with a number of aspects that have a direct

`and indirect bearing on your research topic. Use these aspects

as a basis for developing your theoretical framework. Until you go

through the literature you cannot develop a theoretical framework

and until you have developed a theoretical framework, you

cannot effectively review the literature. Literature pertinent to

your study may deal with two types of information that may be of

universal and more specific( i.e. local trends or specific program)

In writing about such information you should start with the

general information, gradually narrowing down to the specific.

iv. Writing up the literature reviewed:

In order to comply with the first function of literature review such

as to provide theoretical background to your study:

-List the main themes that have emerged while reading literature.

-Convert them into subheadings. These subheadings should be

precise, descriptive of the theme in question, and follow a logical

progression.

-Now, under each subheading, record the main findings with

respect to the theme in question, highlighting the reasons for and

against an argument if they exist, and identify gaps and issues. In

order to comply with the second function of literature review such

as contextualising the findings of your study requires you to very

systematically compare your findings with those made by others.

Quote from these studies to show how your findings contradict,

confirm or add to them. It places your findings in the context of

what others have found out. This function is undertaken when

writing about your findings such as after analysis of your data.

Step3. The formulation of objectives:

Objectives are the goals you set out to attain in your study and

they inform a reader what you want to attain through the study. It

is extremely important to word them clearly and specifically.

Objectives should be listed under two headings:

a) Main objectives (aims)

The main objective is an overall statement of the thrust of

your study. It is also a statement of the main associations

and relationships that you seek to discover or establish.

b) Sub-objectives

The sub-objectives are the specific aspects of the topic that

you want to investigate within the main framework of your

study. They should be numerically listed and wording should

clearly, completely and specifically communicate to your

readers your intention. Each objective should contain only

one aspect of the Study and also use action oriented words

or verbs when writing objectives. The objectives should start

with words such as ‘to determine’, ‘to find out’, ‘to

ascertain’, ‘to measure’, ‘to explore’ etc. The wording of

objectives determines the type of research (descriptive,

Correlational and experimental) and the type of research

design you need to adopt to achieve them for example;-

1) Descriptive studies:

a. To describe the types of incentives provides by Hotel

XYZ to employees in Mumbai.

b. To find out the opinion of the employees about the

medical facilities provided by five star hotels in

Mumbai.

2) Correlational studies:

a. To ascertain the impact of training on employee

retention.

b. To compare the effectiveness of different loyalty

programmes on repeat clientele.

3) Hypothesis –testing studies:

a. To ascertain if an increase in working hours will

increase the incidence of Drug/alcohol abuse.

b. To demonstrate that the provision of company

accommodation to employees in Mumbai hotels will

reduce staff turnover.

Step4. PREPARING THE RESEARCH DESIGN

Research design is the conceptual structure within which research

would be conducted. The function of research design is to provide

for the collection of relevant information with minimal

expenditure of effort, time and money. The preparation of

research design, appropriate for a particular research problem,

involves the consideration of the following:

1. Objectives of the research study.

2. Method of Data Collection to be adopted

3. Source of information—Sample Design

4. Tool for Data collection

5. Data Analysis-- qualitative and quantitative

1. Objectives of the Research Study: Objectives identified to

answer the research questions have to be listed making sure that

they are:

a) Numbered, and

b) Statement begins with an action verb.

2. Methods of Data Collection:

Data refers to ----

There are two types of data

Primary Data— collected for the first time direct from the field

Secondary Data—those which have already been collected and

analysed by someone else.

Methods of Primary Data Collection

OBSERVATION METHOD:

Commonly used in behavioural sciences. It is the gathering of

primary data by investigator’s own direct observation of relevant

people, actions and situations without asking from the

respondent, for example

• A hotel chain sends observers posing as guests into its coffee

shop to check on Cleanliness and customer service.

• A food service operator sends researchers into competing

restaurants to learn menu items prices, check portion sizes and

consistency and observe point-of purchase merchandising.

• A restaurant evaluates possible new locations by checking out

locations of competing restaurants, traffic patterns and

neighborhood conditions.

Observation can yield information which people are normally

unwilling or unable to provide. e.g. Observing numerous plates

containing uneaten portions the same menu items indicates that

food is not satisfactory.

Types of Observation:

1. Structured – for descriptive research

2. Unstructured—for exploratory research

3. Participant Observation

4. Non- participant observation

5. Disguised observation

Limitations:

- feelings, beliefs and attitudes that motivate buying behaviour

and

infrequent behaviour cannot be observed.

-expensive method

Because of these limitations, researchers often supplement

observation with survey research.

SURVEY METHOD

Approach most suited for gathering descriptive information.

Structured Surveys: use formal lists of questions asked of all

respondents in the same way.

Unstructured Surveys: let the interviewer probe respondents and

guide the interview according to their answers.

Survey research may be Direct or Indirect.

Direct Approach: The researcher asks direct questions about

behaviours and thoughts.

e.g. Why don’t you eat at Mac Donalds?

Indirect Approach: The researcher might ask: “What kind of

people eat at

Mac Donald’s?”

From the response, the researcher may be able to discover why

the consumer avoids

MacDonald’s. It may suggest factors of which the consumer is not

consciously aware.

ADVANTAGES:

-can be used to collect many different kinds of information

-Quick and low cost as compared to observation and experimental

method.

LIMITATIONS:

-Respondent’s reluctance to answer questions asked by unknown

interviewers about

things they consider private.

-Busy people may not want to take the time

-may try to help by giving pleasant answers

-unable to answer because they cannot remember or never gave

a thought to what they

do and why

-may answer in order to look smart or well informed.

CONTACT METHODS:

Information may be collected by

Mail

Telephone

Personal interview

Mail Questionnaires:

Advantages:

-can be used to collect large amounts of information at a low cost

per respondent.

-respondents may give more honest answers to personal

questions on a mail

questionnaire

-no interviewer is involved to bias the respondent’s answers.

-convenient for respondent’s who can answer when they have

time

- good way to reach people who often travel

Limitations:

-not flexible

-take longer to complete than telephone or personal interview

-response rate is often very low

- researcher has no control over who answers.

Telephone Interviewing:

- quick method

- more flexible as interviewer can explain questions not

understood by the

respondent

- depending on respondent’s answer they can skip some Qs and

probe more on

others

- allows greater sample control

- response rate tends to be higher than mail

Drawbacks:

-Cost per respondent higher

-Some people may not want to discuss personal Qs with

interviewer

-Interviewer’s manner of speaking may affect the respondent’s

answers

-Different interviewers may interpret and record response in a

variety of ways

-under time pressure ,data may be entered without actually

interviewing

Personal Interviewing:

It is very flexible and can be used to collect large amounts of

information.

Trained interviewers are can hold the respondent’s attention and

are available to

clarify difficult questions.

They can guide interviews, explore issues, and probe as the

situation requires.

Personal interview can be used in any type of questionnaire and

can be conducted

fairly quickly.

Interviewers can also show actual products, advertisements,

packages and observe and

record their reactions and behaviour.

This takes two forms-

Individual- Intercept interviewing

Group - Focus Group Interviewing

Intercept interviewing:

Widely used in tourism research.

-allows researcher to reach known people in a short period of

time.

- only method of reaching people whose names and addresses are

unknown

-involves talking to people at homes, offices, on the street, or in

shopping malls.

-interviewer must gain the interviewee’s cooperation

-time involved may range from a few minutes to several

hours( for longer surveys

compensation may be offered)

--involves the use of judgmental sampling i.e. interviewer has

guidelines as to whom

to “intercept”, such as 25% under age 20 and 75% over age 60

Drawbacks:

-Room for error and bias on the part of the interviewer who may

not be able to

correctly judge age, race etc.

-Interviewer may be uncomfortable talking to certain ethnic or

age groups.

Focus Group Interviewing:

It is rapidly becoming one of the major research tool to

understand people’s thoughts

and feelings.

It is usually conducted by inviting six to ten people to gather for a

few hours with a

trained moderator to talk about a product, service or

organization.The meeting is held

in a pleasant place, and refreshments are served to create a

relaxed environment.

The moderator needs objectivity, knowledge of the subject and

industry, and some

understanding of group and consumer behaviour.

The moderator starts with a broad question before moving to

more specific issues,

encouraging open and easy discussion to bring out true feelings

and thoughts.

At the same time, the interviewer focuses the discussion, hence

the name focus group

interviewing.

-often held to help determine the subject areas on which

questions should be asked in

a later, large-scale, structured-direct interview

Comments are recorded through note taking or videotaped and

studied later to

understand consumer’ buying process.

This method is especially suited for managers of hotels and

restaurants, who have easy

access to their customers.

e.g. Some hotel managers often invite a group of hotel guests

from a particular market

segment to have a free breakfast with them. Managers get the

chance to meet the

guests and discuss what they like about the hotel and what the

hotel could do to make

their stay more enjoyable and comfortable.

The guests appreciate this recognition and the manager gets

valuable information.

Restaurant managers use the same approach by holding

discussion meetings over

lunch or dinner.

Drawbacks:

-Cost: may cost more than telephone survey

-Sampling: group interview studies keep small sample size to

keep time and cost

down, therefore it may be difficult to generalize from the results.

- Interviewer bias.

EXPERIMENTAL METHOD

Also called Empirical Research or Cause and Effect Method, it is a

data-based research, coming up with conclusions which are

capable of being verified with observation or experiment.

Experimental research is appropriate when proof is sought that

certain variables affect other variables in some way. e.g.

Tenderisers (independent variable) affect cooking time and

texture of meat(dependent variable) .

- The effect of substituting one ingredient in whole or in part for

another such as soya flour to flour for making high protein bread.

-Develop recipes to use products.

Such research is characterized by the experimenter’s control over

the variables under study and the deliberate manipulation of one

of them to study its effects.

In such a research, it is necessary to get at facts first hand, at

their source, and actively go about doing certain things to

stimulate the production of desired information.

-Researcher must provide self with a working hypothesis or guess

as to the probable results.

- Then work to get enough facts (data) to prove or disprove the

hypothesis.

-He then sets up experimental designs which he thinks will

manipulate the persons or the materials concerned so as to bring

forth the desired information.

Evidence gathered through experimental or empirical studies

today is considered to be the most powerful support possible for a

given hypothesis. Lowe, Belle; 1958, Experimental Cookery, John

Willey & Sons, New York, pp 34-46

DETERMINING SAMPLE DESIGN

Researchers usually draw conclusions about large groups by

taking a sample of population. A Sample is a segment of the

population selected to represent the population as a whole.

Ideally, the sample should be representative and allow the

researcher to make accurate estimates of the thoughts and

behaviour of the larger population.

Designing the sample calls for three decisions:

1. Who will be surveyed? (The Sample)

The researcher must determine what type of information is

needed and who is most likely to have it.

2. How many people will be surveyed? (Sample Size)

Large samples give more reliable results than small samples.

However it is not necessary to sample the entire target

population.

3. How should the sample be chosen? (Sampling)

Sample members may be chosen at random from the entire

population (probability sample)

• The researcher might select people who are easier to obtain

information from (non probability sample)

The needs of the research project will determine which method is

most effective.

Types of Samples

This kind of sample every individual have equal chance to

be

Probability samples

Simple random sample: Every member of the population has a

known and equal chance of being selected.

Stratified random sample: Population is divided into mutually

exclusive groups such as age groups and random samples are

drawn from each group.

Cluster (area) sample: The population is divided into mutually

exclusive groups such as blocks, and the researcher draws a

sample of the group to interview.

Non probability samples

This is the kind of sampling in which

Convenience sample: The researcher selects the easiest population

members from which to obtain information.

Judgment sample: The researcher uses his/her judgement to select

population members who are good prospects for accurate

information.

Quota sample: The researcher finds and interviews a prescribed

number of people in each of several categories.

TOOL FOR DATA COLLECTION (RESEARCH INSTRUMENTS)

The construction of a research instrument or tool for data

collection is the most important aspect of a research project

because anything you say by way of findings or conclusions is

based upon the type of information you collect, and the data you

collect is entirely dependent upon the questions that you ask of

your respondents. The famous saying about computers- “garbage

in garbage out”- is also applicable for data collection. The

research tool provides the input into a study and therefore the

quality and validity of the output (the findings), are solely

dependent on it.

Guidelines to Construct a Research Tool:

The underlying principle behind the guidelines suggested below is

to ensure the validity of your instrument by making sure that your

questions relate to the objectives of your study.

Step I: Clearly define and individually list all the specific

objectives or research Questions for your study.

Step II: For each objective or research questions, list all the

associated questions that you want to answer through your study.

Step III: Take each research question listed in step II and list the

information required to answer it.

Step IV: Formulate question(s) to obtain this information.

The Questionnaire:

Structured surveys/ interviews employ the use of a questionnaire.

A questionnaire consists of a set of questions presented to a

respondent for answers. The respondents read the questions,

interpret what is expected and then write down the answers

themselves. It is called an Interview Schedule when the

researcher asks the questions (and if necessary, explains them)

and records the respondent’s reply on the interview schedule.

Because there are many ways to ask questions, the questionnaire

is very flexible. Questionnaire should be developed and tested

carefully before being used on a large scale.

There are three basic types of questionnaire:

• Closed –ended

• Open-ended

• Combination of both

Significances of research

Research proposal

Problems encountered by researchers in Tanzania.

SOIL GEOGRAPHY

Introduction

An important factor influencing the productivity of our planet's

various nature of their soils. Soils are vital for the existence of many forms

of life that have evolved on our planet. For example, soils provide vascular

plants with a medium for growth and supply these organisms with most of

their nutritional requirements. Further, the nutrient status of ecosystem’s

soils not only limits consumer type organisms further down the Soil itself is

very complex. It would be very wrong to think of soils as just a collection of

fine mineral particles. Soil also contains air, water, dead organic matter, and

va living organisms. The formation of a soil is influenced by organisms,

climate, topography, parent material, and time. The following items describe

some important features of a soil that help to distinguish it from mineral

sediments.

45%

45%

25%

0.05

Soil Components

water

Mineral parti-cles

Air

0rganic mater

Figure.------. Most soils contain four basic components: mineral particles,

water, air, and organic matter. Organic matter can be further sub- divided

into 80% of humus, 10% of roots and 10% of living organisms. The values

given above are for an average soil.

Organic Activity in soil.

A mass of mineral particles alone do not constitute a true soil. True soils are

influenced, modified and supplemented by living organisms. Plants and

animals aid in the development of a soil through the addition of organic

matter. Fungi and bacteria decompose this organic matter into a semi-

soluble chemical substance known as humus. The large soil organisms

earthworms, beetles, and termites, vertically redistribute this humus within

the mineral matters found beneath the surface of a soil.

Humus is the biochemical substance that makes the upper layers of the soil

become dark. It is coloured dark brown to black. Humus is difficult to see in

isolation because it binds with larger mineral and organic particles. Humus

provides soil with a number of very important benefits:

1. It enhances a soil's ability to hold and store moisture.

2. It reduces the eluviation of soluble nutrients from the soil profile.

3. It is the primary source of carbon and nitrogen required by plants

for their nutrition.

4. It improves soil structure which is necessary for plant growth.

Organic activity is usually profuse in the near surface layers of a soil. For instance,

one cubic centimeter of soil can be the home to more than 1,000,000 bacteria. A

hectare of pasture land in a humid mid-latitude climate can contain more than a

million earthworms and several million insects. Earthworms and insects are

extremely important because of their ability to mix and aerate (ventilate) soil.

Higher porosity, because of mixing and aeration, increases the movement of air and

water from the soil surface to deeper layers where roots reside. Increasing air and

water availability to roots has a significant positive effect on plant productivity.

Earthworms and insects also produce most of the humus found in a soil through the

incomplete digestion of organic matter.

Translocation in soils.

When water moves downward into the soil, it causes both mechanical and chemical

translocations of material. The complete chemical removal of substances from the

soil profile is known as leaching. Leached substances often end up in the

groundwater zone and then travel by groundwater flow into water bodies like rivers,

lakes, and oceans. Eluviation refers to the movement of fine mineral particles (like

clay) or dissolved substances out of an upper layer in a soil profile. The deposition

of fine mineral particles or dissolved substances in a lower soil layer is called

illuviation.

Soil Texture

The texture of a soil refers to the size distribution of the mineral particles found in a

representative sample of soil. Particles are normally grouped into three main

classes: sand, silt, and clay. The following table describes the classification of soil

particles according to size.

Table 1: Particle size ranges for sand, silt, and clay.

Type of Mineral

Particle

Size Range

Sand 2.0 – 0.06 millimetres

Silt 0.06 – 0.002 millimetre

Clay Less than 0.002 millimetres

Clay is probably the most important type of mineral particle found in a soil. Despite

their small size, clay particles have a very large surface area relative to their

volume. This large surface is highly reactive and has the ability to attract and hold

positions. These nutrients are available to plant roots for nutrition. Clay particles are

also somewhat flexible and plastic because of their lattice particles to absorb water

and other substances into their structure.

Soil pH

Soils support a number of inorganic and organic chemical reactions. Many of these

reactions are dependent on some particular soil chemical properties. One of the

most important chemical properties influencing reactions in a soil is pH. Soil pH is

the primarily controlled by the concentration of free hydrogen ions in the soil

matrix. Soils with a relative large concentration of hydrogen ions tend to be acidic.

Alkaline soils have a relatively low concentration of hydrogen ions. Hydrogen ions

are made available to the soil matrix by the dissociation of water, by the activity of

plant root and by many chemical weathering reactions.

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Figure 2: The pH scale. A value of 7.0 is considered neutral. Values higher than 7.0

are increasingly alkaline or basic. Values lower than 7.0 are increasingly acidic. The

illustration above also describes the pH of some common substances.

Soil fertility is directly influenced by pH through the solubility of many nutrients. At

a pH lower than 5.5, many nutrients become very soluble and are leached from soil

profile. At high pH, nutrients become insoluble and plants cannot readily extract

them. Maximum soil fertility occurs in the range 6.0 to 7.2.

Soil Colour

Soils tend to have distinct variations in both vertically and horizontally. The

colouring of soils occurs because of a variety of factors. Soils of the humid tropics

are generally red or yellow because of the oxidation of iron or aluminium

respectively. In the temperate grasslands, large additions of humus cause soils to

be black. The heavy leaching of iron causes coniferous forest soils to be gray. High

water tables in soils cause the reduction of iron, and these soils tend to have

greenish and gray- blue hues. Organic matter colours the soil black. The

combination of iron oxides and organic content gives many soil types a brown

colour. Other colouring materials sometimes present include white calcium

carbonate, black manganese oxides, and black carbon compounds.

Soil Profiles

Most soils have a distinct profile or sequence of horizontal layers.

Generally these layers form horizons which result from the

processes of chemical weathering, eluviation, illuviation and

organic decomposition. Up to five layers can be present in a

typical soil: O, A, B, C and R horizons.

Figure 3: Typical layers found in a soil profile.

The O horizon is the topmost layer of most soils. It is composed

mainly of plant various levels of decomposition and A horizon is

found below the O layer. This layer is composed primarily of

The A horizon has two important characteristics: it is the layer in

which humus and other

organic materials are mixed with mineral particles, and it is a

zone of translocation from

which eluviation has removed finer particles and soluble s

deposited at a lower layer. Thus the A horizon is dark in color and

usually light in texture and

porous. The A horizon is commonly differentiated into a darker

upper horizon or organic

accumulation, and a lower horizon showi

The B horizon is a mineral soil layer which is strongly influenced

by

Consequently, this layer receives material eluviated from the A

horizon. The B horizon also

has a higher bulk density than the A horizon due to its enrichment

of clay particles. The B

horizon may be colored by oxides of iron and

from the A horizon.

or sequence of horizontal layers. Generally, these

weathering, eluviation, illuviation, and

. O, A, B

humus.

mineral

substances, both of which may be

showing loss of material by eluviation.

aluminium or by calcium carbonate illuviated

Page 4

horizons

, organic

B, C, and R

litter at

neral particles.

ubstances, illuviation.

The C horizon is composed of weathered quite variable with

particles ranging in size from clay to not been significantly

influenced by the modification. The final layer in a typical soil

profile is called the of unweather bedrock.

Soil Pedogenesis

Introduction Pedogenesis can be defined as the process of soil

development. Late in the 19th century, scientists Hilgard in the

United States and the Russian Dukuchaev both suggested

independently that pedogenesis was principally controlled by

climate and vegetation. This idea was based on the observation

that comparable soils developed in spatially separate areas when

their climate and vegetation were similar. In the 1940s, Hans

Jenny extended these ideas based on the observations of many

subsequent studies examining the processes involved in the

formation of soils. Jenny believed that the kinds of soils that

develop in a particular area are largely determined by five

interrelated factors: parent material; topography;

and----------------------------

Figure 4: The development of a soil is influenced by five

interrelated factors: organisms, topography, time, parent

material, and climate and parent material. The texture of this

material can be boulders. The C horizon has also pedogenic

processes, translocation, and/or organic R horizon. This soil layer

simply consists s climate; living organisms; time.

Climate plays a very important role in the genesis of a soil. On the

global scale, there is an obvious correlation between major soil

types and the Köppen climatic classification systems major

climatic types. At regional and local scales, climate becomes less

important in soil formation. Instead, pedogenesis is more

influenced by factors like parent material, topography,

vegetation, and time. The two most important climatic variables

influencing soil formation are temperature and moisture.

Temperature has a direct influence on the weathering of bedrock

to produce mineral particles. Rates of bedrock weathering

generally increase with higher temperatures. Temperature also

influences the activity of soil microorganisms, the frequency and

magnitude of soil chemical reactions, and the rate of plant

growth. Moisture levels in most soils are primarily controlled by

the addition of water via precipitation minus the losses due to

evapotranspiration. If additions of water from precipitation

surpass losses from evapotranspiration, moisture levels in a soil

tend to be high.

If the water loss due to evapotranspiration exceeds inputs from

precipitation, moisture levels in a soil tend to be low. High

moisture availability in a soil promotes the weathering of bedrock

and sediments, chemical reactions, and plant growth. The

availability of moisture also has an influence on soil pH and the

decomposition of organic matter.

Living Organisms have a role in a number of processes involved in

pedogenesis including organic matter accumulation, profile

mixing, and biogeochemical nutrient cycling. Under equilibrium

conditions, vegetation and soil are closely linked with each other

through nutrient cycling. The cycling of nitrogen and carbon in

soils is almost completely controlled by the presence of animals

and plants. Through litterfall and the process of decomposition,

organisms add humus and nutrients to the soil which influences

soil structure and fertility.

Surface vegetation also protects the upper layers of a soil from

erosion by way of binding the soils surface and reducing the

speed of moving wind and water across the ground surface.

Parent Material refers to the rock and mineral materials from

which the soils develop.

These materials can be derived from residual sediment due to the

weathering of bedrock or from sediment transported into an area

by way of the erosive forces of wind, water, or ice.

Pedogenesis is often faster on transported sediments because the

weathering of parent material usually takes a long period of time.

The influence of parent material on pedogenesis is usually related

to soil texture, soil chemistry, and nutrient cycling.

Topography generally modifies the development of soil on a local

or regional scale. Pedogenesis is primarily influenced by

topography's effect on microclimate and drainage.

Soils developing on moderate to gentle slopes are often better

drained than soils found at the bottom of valleys. Good drainage

enhances an number of pedogenic processes of illuviation and

eluviation that are responsible for the development of soil

horizons. Under conditions of poor drainage, soils tend to be

immature. Steep topographic gradients inhibit the development of

soils because of erosion. Erosion can retard the development

through the continued removal of surface sediments. Soil

microclimate is also influenced by topography. In the

Northern Hemisphere, south facing slopes tend to be warmer and

drier than north facing slopes. This difference results in the soils

of the two areas being different in terms of depth, texture,

biological activity, and soil profile development.

Time influences the temporal consequences of all of the factors

described above. Many soil processes become steady state

overtime when a soil reaches maturity. Pedogenic processes in

young soils are usually under active modification through

negative and positive feedback mechanisms in attempt to

achieve equilibrium.

Principal Pedogenic Processes

A large number of processes are responsible for the formation of

soils. This fact is evident by the large number of different types of

soils that have been classified by soil scientists.

However, at the macro-scale we can suggest that there are five

main principal pedogenic processes acting on soils. These

processes are laterization, podzolization, calcification, salinization,

and gleization.

Laterization is a pedogenic process common to soils found in

tropical and subtropical

environments. High temperatures and heavy precipitation result

in the rapid weathering of

rocks and minerals. Movements of large amounts of water

through the soil cause eluviation and leaching to occur. Almost all

of the byproducts of weathering, very simple small compounds or

nutrient ions, are translocated out of the soil profile by leaching if

not taken up by plants for nutrition. The two exceptions to this

process are iron and aluminum compounds.

Iron oxides give tropical soils their unique reddish coloring. Heavy

leaching also causes these soils to have an acidic pH because of

the net loss of base cations. Podzolization is associated with

humid cold mid-latitude climates and coniferous vegetation.

Decomposition of coniferous litter and heavy summer

precipitation create a soil solution that is strongly acidic. This

acidic soil solution enhances the processes of eluviation and

leaching causing the removal of soluble base cations and

aluminum and iron compounds from the A horizon. This process

creates a sub-layer in the A horizon that is white to gray in color

and composed of silica sand.

Calcification occurs when evapotranspiration exceeds

precipitation causing the upward movement of dissolved alkaline

salts from the groundwater. At the same time, the movement of

rain water causes a downward movement of the salts. The net

result is the deposition of the translocated cations in the B

horizon. In some cases, these deposits can form a hard layer

called caliche. The most common substance involved in this

process is calcium carbonate. Calcification is common in the

prairie grasslands.

Salinization is a process that functions in the similar way to

calcification. It differs from calcification in that the salt deposits

occur at or very near the soil surface. Salinization also takes place

in much drier climates.

Gleization is a pedogenic process associated with poor drainage.

This process involves the accumulations of organic matter in the

upper layers of the soil. In lower horizons, mineral layers are

stained blue-gray because of the chemical reduction of iron.

Soil Classification

Introduction

Soil Classification Systems have been developed to provide

scientists and resource managers with generalized information

about the nature of a soil found in a particular location. In

general, environments that share comparable soil forming factors

produce similar types of soils. This phenomenon makes

classification possible.

Over the past century, various soil classifications have been

devised in the United States and other countries. As the

knowledge of soil characteristics and processes has become more

sophisticated. Several different systems have been developed in

United States, Canada, United Kingdom, Russia, France and

Australia. Moreover, United Nations organisations agencies have

their own classification schemes. As a matter of example we will

discuss about United States Soil Classification System.

United States Soil Classification System

The first formal system of soil classification was introduced in the

United States by Curtis F. Marbut in the 1930s. This system,

however, had some serious limitations, and by the early 1950s

the United States Soil Conservation Service began the

development of a new method of soil classification. The process of

development of the new system took nearly a decade to

complete. By 1960, the review process was completed and the

Seventh Approximation Soil Classification System was introduced.

Since 1960, this soil classification system has undergone

numerous minor modifications and is now under the control of

Natural Resources

Conservation Service (NRCS), which is a branch of the

Department of Agriculture. The current version of the system has

six levels of classification in its hierarchical structure. The major

divisions in this classification system, from general to specific,

are: orders, suborders, great groups, subgroups, families, and

series. At its lowest level of organization, the U.S. system of soil

classification recognizes approximately 15,000 different soil

series.

The most general category of the NRCS Soil Classification System

recognizes eleven distinct soil orders: oxisols, aridsols, mollisols,

alfisols, ultisols, spodsols, entisols, inceptisols, vertisols, histosols,

and andisols.

Oxisols develop in tropical and subtropical latitudes that

experience an environment with high precipitation and

temperature. The profiles of oxisols contain mixtures of quartz,

kaolin clay, iron and aluminum oxides, and organic matter. For

the most part they have a nearly featureless soil profile without

clearly marked horizons. The abundance of iron and aluminum

oxides found in these soils results from strong chemical

weathering and heavy leaching. Many oxisols contain laterite

layers because of a seasonally fluctuating water table.

Aridsols are soils that develop in very dry environments. The main

characteristic of this soil is poor and shallow soil horizon

development. Aridsols also tend to be light colored because of

limited humus additions from vegetation. The hot climate under

which these soils develop tends to restrict vegetation growth.

Because of limited rain and high temperatures soil water tends to

migrate in these soils in an upward direction. This condition

causes the deposition of salts carried by the water at or near the

ground surface because of evaporation. This soil process is of

course called salinization.

Mollisols are soils common to grassland environments. In the

United States most of the natural grasslands have been converted

into agricultural fields for crop growth. Mollisols have a dark

colored surface horizon, tend to be base rich, and are quite fertile.

The dark color of the A horizon is the result of humus enrichment

from the decomposition of litterfall.

Mollisols found in more arid environments often exhibit

calcification.

Alfisols form under forest vegetation where the parent material

has undergone significant weathering. These soils are quite

widespread in their distribution and are found from southern

Florida to northern Minnesota. The most distinguishing

characteristics of this soil type are the illuviation of clay in the B

horizon, moderate to high concentrations of base cations, and

light colored surface horizons.

Ultisols are soils common to the southeastern United States. This

region receives high amounts of precipitation because of summer

thunderstorms and the winter dominance of the mid-latitude

cyclone. Warm temperatures and the abundant availability of

moisture enhances the weathering process and increases the rate

of leaching in these soils. Enhanced weathering causes mineral

alteration and the dominance of iron and aluminum oxides. The

presence of the iron oxides causes the A horizon of these soils to

be stained red. Leaching causes these soils to have low quantities

of base cations.

Spodsols are soils that develop under coniferous vegetation and

as a result are modified by podzolization. Parent materials of

these soils tend to be rich in sand. The litter of the coniferous

vegetation is low in base cations and contributes to acid

accumulations in the soil.

In these soils, mixtures of organic matter and aluminum, with or

without iron, accumulate in the B horizon. The A horizon of these

soils normally has an eluvial layer that has the color of more or

less quartz sand. Most spodosols have little silicate clay and only

small quantities of humus in their A horizon.

Entisols are immature soils that lack the vertical development of

horizons. These soils are often associated with recently deposited

sediments from wind, water, or ice erosion. Given more time,

these soils will develop into another soil type.

Inceptisols are young soils that are more developed than entisols.

These soils are found in arctic tundra environments, glacial

deposits, and relatively recent deposits of stream alluvium.

Common characteristics of recognition include immature

development of eluviation in the A horizon and illuviation in the B

horizon, and evidence of the beginning of weathering processes

on parent material sediments.

Vertisols are heavy clay soils that show significant expansion and

contraction due to the presence or absence of moisture. Vertisols

are common in areas that have shale parent material and heavy

precipitation. The location of these soils in the United States is

primarily found in Texas where they are used to grow cotton.

Histosols are organic soils that form in areas of poor drainage.

Their profile consists of thick accumulations of organic matter at

various stages of decomposition.

Andisols develop from volcanic parent materials. Volcanic

deposits have a unique process of weathering that causes the

accumulation of allophane and oxides of iron and aluminum in

developing soils.

Seminar Question

What can you learn about a soil from its colour?

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