SURVEYING I

UNIT I by

R.GOPALAKRISHNAN

Asst.Professor in Civil Engineering, Dept. of Civil Engineering,

Sri Venkateswara College of Engineering.

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UNIT I FUNDAMENTALS AND CHAIN SURVEYING

Definition – Classifications – Basic principles- Equipment and accessories for ranging and chaining- Methods of ranging – well conditioned triangles errors in linear measurement and their corrections – obstacles – Traversing plotting applications – enlarging the reducing the figures – Areas enclosed by straight line irregular figures – Digital planimeter.

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INTRODUCTION AND OVERVIEW

Objectives Appreciate the importance of surveying State the objectives of surveying Explain the basic principles of surveying Classify surveys according to instruments, methods,

purpose and place Explain the construction and working of different types

of scales

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AGENDA

Objectives of Surveying

Basic Principles

Basic Terminology

Classification of Surveys

General

Plans and Maps

Scales

Errors

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Definition

• Surveying is the art of determining the relative positions of different objects on the surface of the earth by measuring the horizontal distances between them, by preparing a map to a suitable scale.

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OBJECTIVES OF SURVEY

Collect and record data of points on the surface of the earth

Compute areas and volumes

Prepare plans and maps

Lay out engineering works using survey data

Check the accuracy of laid out works

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Uses of surveying

• To prepare a topographical map this shows the hills, valley, rivers, villages, town, etc, of a country.

• To prepare a cadastral map showing the boundaries of fields houses, and other properties.

• To prepare an engineering map to show details like roads, railways, canals, etc.

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Contd….

• To prepare military map showing roads and railways, communication with different parts of country.

• To prepare contour map and to determine capacity of a reservoirs and ton find the best possible route for roads, railways etc.

• To prepare archeological map including places where ancient relics exist.

• To prepare a geological map showing areas including underground resources

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BASIC PRINCIPLES

1. Working from whole to part

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BASIC PRINCIPLES

2. Locating points by independent measurements

Points can be located by rectangular coordinates

Polar coordinates

By measuring two angles

Angular and linear measurements

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BASIC PRINCIPLES

• Locating points by independent measurements

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BASIC DEFINITIONS

Level line, horizontal line and plumb line

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BASIC DEFINITIONS

Earth’s Magnetism

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CLASSIFICATION OF SURVEYS

Plane Survey - When the survey area is small, the curvature of the earth is ignored. Difference between arc and chord is small.

Geodetic Survey – High precision survey where survey area is large and curvature of earth is taken into account. Many other correction in measured quantities are done for higher precision.

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CLASSIFICATION OF SURVEYS

Instrument based Survey • Chain survey • Compass survey • Plane Table Survey • Theodolite Survey • Levelling • Tacheometry • EDM survey • Total Station Survey • Remote sensing, Satellite-based Survey

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CLASSIFICATION OF SURVEYS

Method-based Surveys

• Triangulation

• Trilateration

• Traversing

• Levelling

• Tacheometry

• Trigonometric Levelling

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CLASSIFICATION OF SURVEYS

Purpose-based surveys

• Reconnaissance

• Preliminary Survey

• Engineering Survey

• Geographical Survey

• Mine Surveys

• Route Surveys

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CLASSIFICATION OF SURVEYS

Purpose-based surveys

* Location Surveys

• Geological Surveys

• Defence Surveys

• Archeological Surveys

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CLASSIFICATION OF SURVEYS

Place-based Surveys

• Land Survey

• Hydrographic Survey

• Aerial Survey

• Underground Survey

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CONTROLS

Horizontal Control – Establishing points with great precision using highly precise equipment; Such points are used for further detailed surveys.

Vertical Control – Establishing points of known elevation, called Bench Marks, using precise instruments and methods. The Datum surface is the mean sea level.

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SURVEY INSTRUMENTS

Survey instruments are delicate and sensitive.

Care in using instruments

• Follow manufacturer’s instructions

• Keep instrument in the box or cover properly

• Protect from sun and rain

• Take care of optical parts

• Proper use of instruments in field.

• Proper, frequent adjustment.

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QUALITIES OF GOOD SURVEYOR

• Sound knowledge of theory

• Knowledge of instruments, limits of precision, possible errors and maintenance

• Field practice, proficiency, accuracy and judgment

• Leadership qualities

• Good professional conduct

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Measurement of Distance

• Linear measurement is the basis of all surveying and even though angles may be read precisely, the length of at least one line in a tract must be measured to supplement the angles in locating points.

• Old surveys were often measured using a

Surveyors Chain. These were literally chains made up of 100 links. Each Chain was 66 feet long. Each link was 0.666 of a foot.

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Units of Measurement

• Acre - The (English) acre is a unit of area equal to 43560 square feet, or 10 square chains. A square mile is 640 acres. The Scottish acre is 1.27 English acres.

• Chain - Unit of length usually understood to be Gunter's chain, from the heavy metal chain of 100 links that was used by surveyors to measure property bounds.

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Units of Measurement

• Hectare - Metric unit of area equal to 10,000 square meters, or 2.471 acres.

• Link - Unit of length equal to 1/100 chain (7.92 inches).

Engineer's Chain - A 100 foot chain containing 100 links of one foot a piece.

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Linear Measurements

Accessories or Equipments:

1. Ranging rods

2. Chains – Metric Chain, Engineer’s chain, Gunter’s Chain, Revenue Chain, Steel band.

3. Metric chain – 100 links – each 0.2m, Talleys – every 10 links

20m chain or 30m chain.

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Contd..

• Steel band : It consists of ribbon of steel width of 16mm (length 20m or 30m)

• Engineer’s chain : 100 ft long (100 links)

• Gunter’s chain : 66 ft long (100 links)

• Revenue Chain : 33ft long (16 links)

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• Tapes: Cloth or linen tape, metallic tape (reinforced with brass or copper), Steel tape, Invar tape ( Alloy of steel – 64% and metal 36%)

Arrows : 4mm diameter ( 400mm length)

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PLANS AND MAPS

Plans and maps are graphical representations.

Plans and maps are projections of a spherical surface on a plane.

Distortions occur during such representations

In the case of small areas, such distortions are small and accepted.

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Scales

The ratio by which the actual length of the object is reduced or increased is known as Scales.

Full size scale:

If the actual length of the object is shown on the drawing the scale is said to be full size scale

Reducing scale:

If the actual length of an object is reduced in order to accommodate on the drawing sheet the scale is said to be a reducing scale.

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Contd.. Increasing or Enlarging scale:

If the actual length of an object is enlarged so as to bring details more clearly on the drawing, the scale used is called enlarging scale.

Representative fraction:

The ratio of the distance on the drawing to the corresponding actual length of the object is known

representative fraction.

RF = Distance on drawing of object

Corresponding actual distances of the object

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Types of Scales:

1. Plain

2. Diagonal

3. Comparative scale

4. Vernier scale

Plain scale:

The scale used to represent two successive units. (eg. Metre, decim, km, hectam

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Diagonal scale:

The scale used to represent 3 successive units or one unit and fraction up to second place of decimals (eg km, hectam, decim; metre, decim, cm)

Length of the scale:

Length of the scale should be calculated according to max.length shown. Max. length is not given, it is assumed within (10 – 15cm) so that , max. distance is divisible by 10 or 100.

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Problem 1

A Plan represents an area of 93750 Sq.m and measures 6 x 6.25 cm. Find the scale of the plot and indicate through a sketch how suitable scale can be constructed to read up to 1m in the plan

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Problem 2

A 1.2 km long road is indicated in a map by a length of 30 cm. Find the scale of the plot and indicate through a sketch how suitable scale can be constructed to read up to 1m in the map.

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SCALES

Scale representation is

i) as 1 cm = 10 m.

ii) As representative fraction 1/1000

iii) Or as graphical representation

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PLAIN SCALE STANDARDS

Designation Scale values RF values

A Full size, 50 cm to 1 m 1/1, 1/2

B 40 cm = 1m, 20 cm =

1 m

1/2.5, 1/5

C 10 cm = 1m, 5 cm = 1

m

1/10, 1/20

D 2 cm = 1 m, 1 cm = 1

m

1/50, 1/100

E 5 mm = 1m, 2 mm = 1

m

1/200, 1/500

F 1 mm = 1m, 0.5 mm =

1m

1/1000, 1/2000

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DIAGONAL SCALE

Construction of diagonal scale

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DIAGONAL SCALE

Construction of Diagonal scale

Is based on the principle of similar triangles

Can measure three dimensions like units, tenths and hundredths.

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DIAGONAL SCALE STANDARDS

Designation Length RF

A 150 cm 1/1

B 100 cm 1/100000, 1/25000

1/25000,

C 50 cm 1/100000, 1/50000

1/25000,

D 150 cm 1/100000, 1/8000, 1/4000

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