CHAPTER 1

1.0 INTRODUCTION:

An art and science of determining the relative position of point on above or beneath the

surface of the earth by means of angular and linear measurements is defined as

Surveying. It is the most important subject matter before and during all engineering

works like civil engineering works such as designing and construction of highways, water

supply systems, irrigation projects, buildings etc. The application of surveying requires

the knowledge of mathematics, physics, and to some extent, astronomy. Surveying

basically consists of collecting data and information about the terrain of the topography of

the proposed area, land use, property and the state boundaries, the charting of coastlines

and navigable streams and lakes, the location of valuable mine deposits etc. It is a

framework for the conception, design and execution of any engineering work. The

information about these features are gathered by measuring the horizontal and vertical

distances between the objects, by measuring the angle between the lines and by

establishing points by predetermined angular and linear measurements. The actual

measurements are accompanied by mathematical calculations for determining distances,

angles, directions, locations, elevations, areas and volumes. The information thus

collected is then portrayed graphically by the construction of maps, profiles, cross-

sections and other diagrams.

The main objectives of surveying courses allocated for civil engineering students

is to promote them the basic knowledge of different surveying techniques relevant to civil

engineering works in their professional practice. The completion of all surveying courses

including 15 days survey camp work organized by the Department of Civil Engineering,

Khwopa Engineering College will give better enhancement to students to use all

surveying technique covered in lecture classes.

Survey Camp is a part of the third-year Bachelor's degree in Civil Engineering

course, third year first semester, carrying a total of 100 marks. The total duration of the

survey camp was 15 days, from 12thKartikto 26thKartik 2069.

The work done during the camp duration can be categorized into three main

projects:

1. Topographical survey

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2. Bridge site survey

3. Road alignment survey

This is a detail report of the works, which were performed by group no. B3,

having fivemembers, during the camp period. It briefly explains the working procedures

and technique used by this group during that camp period. In addition, it also contain

observations, calculations, methods of adjustment of error, main problem faced during

work and their solution, results of all calculations and their assessments with some

comments is presented in a concise form.

1.1 OBJECTIVES OF SURVEY CAMP:

The main objective of this survey camp allocated for civil engineering students is to

consolidate and update their basic knowledge of different surveying techniques relevant

to civil engineering works. Working in actual field conditions enhances their theoretical

and practical knowledge and increases their confidence that is beneficial to their

professional practice in the near future.

The main objectives of the survey camp are as follows:

To become familiar with the surveying problems that are arise during the field

works.

To became familiar with the parts of the instruments, their functions and handling

the surveying instruments for its use in surveying.

To become familiar with the spirit and importance of teamwork, as surveying is

not a single person work.

To complete the given project in scheduled time and thus knows the value of time.

To collect required data in the field in systematic ways.

To compute and manipulate the observed data in the required accuracy and

present it in diagrammatic and tabular form in order to understand by other

engineers and related personnel easily.

To tackle the mistake and incomplete data from the field while in office work.

To know the complete method of report preparation.

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1.2METHODOLOGY: 

The methodology of the surveying is based on the principle of surveying, which includes:

•Working from Whole to the Parts 

•Independent Check  

• Accuracy Required  

• Consistency in Work 

1.3INDEX MAP/LOCATION MAP:

1.4 PROJECT AREA: 

The description of the project area is as follows:

Nepal Electricity Authority Training Center (NEATC), Kharipati,Bhaktapur is about 18 k

m North East of Kathmandu. The area to us for survey is about 200 ropanis of land with

varieties of land.

(i.e. jungle, vegetation, human settlement etc) .The details of the area is as follows

Country: ‐ Nepal  

Region: ‐   Central Development Region

Zone: ‐      Bagmati 

District: ‐   Bhaktapur    

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Location: ‐ NEATC premises for Topographical Survey Nagarkot,Dolalghat of

Kavre for Bridge Site Survey NEATC premises for Road Alignment Survey.

1.5 LOCATION ANDACCESSIBILITY:

Our Survey Camp site was located near about 27º41'16"N and 85º27'20"E, at the altitude

of 1362 m and about 16 km East of Kathmandu. The area allocated to us for survey is

about 292065.62 sq m. of land with variable land features and almost all the man made

mentors like road, sports ground building and pond etc.

It took about twenty minutedriveto reach Kharipati from Libali, Bhaktapur. The project

site is situated in the range of about 1330 m. above mean sea level.

i) Region: Kharipati VDC and Nagarkot VDC

ii) District: Bhaktapur

iii) Zone: Bagmati

1.6TOPOGRAPHY AND GEOLOGY

Kharipati has gentle and steep topography differing from places to places. The area

contains ground features ranging from steep slopes to flat grounds. These features were

shown by contours. The geological structure is in good condition, so there is no any

geological disasters and eruption. Soil types are found similar to any other part of

Bhaktapur i.e. soft clay, irrigated by river and well suitable for cultivation. And the bridge

site, Cha Khola perennial however the flow decreases considerably during dry seasons.

Different types of rock exposure are seen most of them are amphibolites, gneiss,

sandstones, schists etc.

1.7RAINFALL,CLIMATE AND VEGETATION:

The weather is moderate between autumn seasons. During the camp period temperature

was fluctuating from maximum to minimum of it just similar to the annual temperature

variation and rain fall around Kathmandu valley is:-

Temperature: maximum 25oC to minimum 4oC

The atmosphere was cool in the morning with high value of humidity.

Most of the empty spaces of the project area were full of vegetation but without

cultivated land except for some land around canteen area. Ordinary grassland covered

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most of the areas. Presence of few plants, trees and bushes made environment green and

pleasant.

1.8 DESCRIPTION OF WORK 

Topographic Survey: -

Objective: To make the topographic map with engineering requirements.

Location: premises of NEATC

Salient Features: Total Numbers of major traverse stations = 14

: Total numbers of minor traverse stations = 2

: Contour Interval = 1m

: Scale of map = 1:1000in major, 1:500 in minor

: Detailing = Total Station

Check: Plane Table

Leveling: -

Objectives: Two pegs test was carried out. As our auto level was within precision no

correction was needed.

Location: premises of NEATC

Silent Features: Transfer of RL from BM to CP1

Transfer of RL from CP1 to major station

Transfer of RL from major station to minor station

Bridge Site Survey:

Objectives: To fix the bridge axis and topographic map of the existing site along with the

L-section, X-section of river.

Location: Dolalghat, Kavre

Salient Features: No. of stations used :Topographic map at 1:200

Contour Interval 1m

Cross section up to 150m on upstream and 75m on downstream at 10m

interval.

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Road alignment:

- Objectives: to make L-section, X-section and topographic map of area of the site

- Location: premises of NEATC

- Salient feature: Map scale = 1:500

Cross section at every BC, EC & MC and 20m interval with minimum

of 5m and 10m left and right details.

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CHAPTER 2

2.0TOPOGRAPHICAL SURVEY:

The survey in which the position of natural and artificial features on both plan and

elevation are determined is known as topographical survey. From the survey data,

topographic maps that depict these natural and cultural features are produced using

various types of lines and conventional symbols. Topographic is simply the graphical

representation of positions of the earth's surface. In other words topographical surveying

is the process of determining the positions of natural and artificial features of the locality

by means of conventional signs up on a topographical map. Topographic surveys are

three-dimensional; they provide the techniques of plane surveying and other special

techniques to establish both horizontal and vertical control. Hence the fieldwork in a

topographical surveying consists of three parts.

It establishes both horizontal and vertical control.

It locates the contours.

It also locates the details such as rivers, streams, lakes, roads, houses, and

trees etc.

2.1OBJECTIVES

The main objective of topographical survey is to prepare the topographical map of

the given area with horizontal control and vertical control on required accuracy.

2.2. BRIEF DESCRIPTION OF THE AREA

The area, where surveying was performed, is situated at NEA training center,

Kharipati, Bhaktapur. The major traverse was run throughout the land area, which cover

the full area of the NEA. Our objective was to prepare a topographic map of the given

small area, which is a part of the NEA area. So, we were assigned to prepare the

topographic map of the area including the two Dormitories and all the natural and

manmade features that may come in the general survey work. The two identical and

symmetrical Dormitories were situated at southern side of NEA Training Center building.

The rest of the area includes grassland with bushes near the walls of the site and backyard

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of the dormitories. The far south-west area consists closed exit gate with an guard house

and a drain pond opposite to it.

2.3 NORMS (TECHNICAL SPECIFICATIONS)

o Reconnaissance was conducted at first. A close traverse (major and minor) around

the perimeter of the area was formed by making traverse stations. In the selection

of the traverse station, it was made sure that the stations were inter-visible and

maintained the ratio of maximum traverse leg to minimum traverse leg 3:1 for

minor traverse and 2:1 in the case of major traverse.

o The traverse legs were measured in the forward and reverse directions by Total

station note that discrepancy between forward and backward measurements

should be greater than 1:2000.

o Traverse angles were measured on two sets (both 0 set and 90) of reading by Total

station. Note the difference between the mean angles of two sets reading should be

within 1’.

o Determined the R.L. of traverse stations by fly leveling from the given arbitrary

B.M. Perform two-peg-test before the start of fly leveling. Note the collimation

error should be less than 1:10000. Maintain equal foresight and back sight

distances to eliminate collimation error. Permissible error for fly leveling is

25√k mm, Where k =distance (km)

o R.L of B.M. = 1340.000m

o Balance the traverse. The permissible angular error for the sum of interior angles

of the traverse should be less than ±√n x 1 minute for Major Traverse and ±√n x

1.5 minutes for Minor Traverse (n = no of traverse station). For major and minor

traverse the relative closing error should be less than 1:2000 and 1:1000

respectively.

o After computing the coordinate of the control points, they are ready to be plotted.

Full size drawing sheets i.e. A1 size is divided into gridlines of 5cm square. The

gridlines are made with the help of beam compass. Both the major and minor

traverse is plotted to 1:1000 for major traverse and 1:500 for minor traverse. The

plotted traverse is made at the centre of the sheet with the help of least coordinates

and high coordinates.

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o Then detail survey of the given sub area was carried out by tachometry with

reference to the major and minor traverse, which have been already plotted. Use

conventional symbols for plotting.

2.4 EQUIPMENTS:

Theodolite

Staffs and ranging rods

Tapes

Plumb bob

Level

Compass

Plane table

Alidade

Compass

Spirit level

Marker

Hammer

Pegs

Arrows

Total Station

2.5 METHODOLOGY

The methodology of surveying is based on the principle of surveying which are listed as

below:-

Working from whole to a part

Independent check

Consistency of work

Precision maintained

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2.5.1 RECONNAISSANCE (RECCE)

Recce means the exploration or scouting of an area. In survey, it involves walking around

the survey area and roughly planning the number of stations and the position of the

traverse stations. Recce is primarily done to get an overall idea of the site. This helps to

make the necessary observations regarding the total area, type of land, topography,

vegetation, climate, geology and inter-visibility conditions that help in detailed planning.

The following points have to be taken into consideration for fixing traverse stations.

The adjacent stations should be clearly inter-visibility

The whole area should include the least number of stations possible.

The traverse station should maintain the ratio of maximum traverse leg to minimum

traverse leg 1:2 for major and 1:3 for minor.

The steep slopes and badly broken ground should be avoided as far as possible, which

may cause inaccuracy in tapping.

The stations should provide minimum level surface required for setting up the

instrument.

The traverse line of sight should not be near the ground level to avoid the refraction.

Taking the above given points into consideration, the traverse stations were fixed. Thus,

permanent fixing of the control points completes recce. So for better planning, detailed inspection

of the area to be surveyed (NEA) was performed by the method known as

RECONNANISSANCE (RECCE) survey.

2.5.2 TRAVERSING

Traversing is a type of surveying connecting number of survey lines forming the

framework. It is also a method of control surveying. This survey consists of the

measurement of a) Angles between successive lines or bearings of each line.

b) The length of each line.

The directions and the lengths of the survey lines are measured with the help of total

station. If the co-ordinates of the first station and the bearing of the first line are known,

the co-ordinates of all successive points can be computed as follows:

XB = XA + L CosӨ Where, L=Length of traverse leg

YB = YA + L SinӨ Ө=Bearing of that leg

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There are two types of traverse. They are as follows:

1. CLOSE TRAVERSE

If the figure formed by the lines closes at a station i.e. if they form a

polygon or it starts and finishes at the points of known co-ordinates then the

traverse is called closed traverse.

2. OPEN TRAVERSE

If a traverse starts and finishes at points other than the starting point or

point of known co-ordinates, then the traverse is called open traverse.

(i) Closed Loop Traverse (ii )Closed (Linked) Traverse (iii) Open Traverse

Fig: Types of Traverses

BALANCING THE TRAVERSE:

During the computation of the traverse, we need to balance the traverse because of the

different errors in the field measurement. There are different methods of adjusting a

traverse such as:

Bowditch method

Transit method

Graphical method

Axis method

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The basis of these methods is on the assumptions that the errors in linear

measurements are proportional to ‘L’ and that the errors in angular measurements are

inversely proportional to ‘L’ where L is the length of a traverse leg.

The Bowditch’s Rule is commonly used to balance a traverse where linear and

angular measurements are of equal precision. The total error in latitude and in the

departure is distributed in proportion to the lengths of sides. The Bowditch rule gives the

correction as,

CorrectionToLat .or Dept=Total Error inLat .(orDept . )∗(Lengthof That Leg)

Perimeterof thatTraverse

2.5.3 ADJUSTMENT OF ANGULAR ERROR AND BEARING:

The error (e) in a closed traverse due to bearing may be determined by comparing

the two bearings of the last line as observed at the first and last stations of traverse. If the

closed traverse, has N number of sides then,

Correction for the first line = e/N

Correction for the second line = 2*(e/N)

And similarly, correction for the last line = N*(e/N) = e

In a closed traverse, by geometry, the sum of the interior angles should be equal to

(2n-4)*90˚ where n is the number of traverse stations. If the angles are measured with the

same degree of precision, the error in the sum of the angles may be distributed equally

among each angle of the traverse.

2.5.4 DISCREPANCY AND LINEAR MISCLOSURE:

In order to measure the lengths of the sides of the traverse, two ways measurement

(forward and backward) is done with the help of total station.

The difference in values obtained by forward and backward measurement is called

discrepancy

. The reciprocal of mean of the two measurements divided by the discrepancy is called

precision.

Both the discrepancy and the precision for each traverse leg should be within the given

limits.

Mathematically,

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Discrepancy = Forward length - Backward length &,

Linear precision = 1 / (Mean length / Discrepancy)

2.5.5 MAJOR TRAVERSE

Traversing is a type of survey in which a number of connected survey lines form a

framework enclosing the area to be surveyed. Working from whole to part is the

principle. So, the whole area is enclosed by number of control points of which details are

necessary. The skeleton of lines joining those control points, which covers the whole

entire area, is called Major Traverse. Work on Major traverse must be precise. So two-set

of reading should be taken for Major Traverse. For convenience, the readings are taken

by setting the theodolite at 0o0'0" for one set and 90o00'00" for the second.

In the KHEC Survey Camp, two traverses - major and minor had to be established. The

major traverse had 14 control stations including two given control points and the ends of

the given control line. The control stations were named as M1,M2… and so on CP1 and

CP2 were the two given control points and the leg ratio of maximum traverse leg to

minimum traverse leg was maintained within 1:2. The discrepancy in length between the

forward measurements and the backward measurements of all the traverse legs was within

1:2000. Four sets of total station readings were taken for measuring the horizontal

traverse angles. The difference between the mean angles of two sets of readings was

within a minute1’ or all the angles.

2.5.6 MINOR TRAVERSE

It is not sufficient to detail the area by enclosing with the help of major traverse.

Minor traverse is that one which runs through the area to make detailing easy. Minor

Traverse covers only small area. Less precise work than that of major traverse is

acceptable so that single set reading is sufficient minor traverse. The minor traverse had 2

control stations and enclosed the dormitories and its premises. The control stations were

named as m1 and m2 on along with two control stations common for both the major and

the minor traverses. The leg ratio of maximum traverse leg to minimum traverse leg was

maintained within 1:3. The discrepancy in length between the forward measurements of

all the traverse legs was within 1:1000.

2.5.7 Orientation

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Orientation is the process of determining the position or location of unknown points with

the help of location of known points.

In other words orientation is the analytic analysis in which coordinate (x,y,z) of unknown points

is fixed out by sighting known points from two or three points whose coordinate are already

established or known.

Generally,depending upon he basis setting up the instrument, there are two method of

orientation ,which are as follows:

A) Intersection

B) Resection

A)Resection

It is the method of deterring the position of the point by observing horizontal

direction from it to previously fixed points. It is an ideal method of placing additional

control points around a survey area in positions eminently suitable for detailing or setting

out.

Analytical method of resection are

I. Two points problem method

II. Three points problem method A

Collin’s method

(Ø-45°) method a m2

γ

β α

B

b

c

C

Known points are:

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Co-ordinate of M12 = A (2676789.625, 3301777.737) α= 222°31’27”

Coordinate of CP = B (2676866.898, 3301818.333) β = 89°41’0’’

Coordinate of M11 = C (2676837.184, 3301678.509) γ=47°47’3’’

Calculation of Bearings:

Bearing of AB = tan-1 (2676866.898−2676789.625)(3301818.333−3301777.737) = 61°59’39"

Similarly,

Bearing of BA=241°59’39"

Bearing of AC=171°29’49"

Bearing of CA=351°29’49"

Bearing of CB=23°59’13"

Bearing of BC=203°59’13"

On solving this, we get

< a=bearing of AC- bearing of AB=109°30’10"

Similarly,

< b=38°0’26"

< c=32°29’24"

K1= 1

cot<a−cot ¿α = -0.692

K2= 1

cot<b−cot ¿ β = 0.784

K3= 1

cot<c−cot ¿ γ = 1.507

Finally,

Y=Y= K1Y 1+K2Y 2+K 3Y 3

K 1+K 2+K 3 = 3301704.368

X =K1 X 1+K 2 X2+K 3Y 3

K1+K 2+K 3 =2676841.494

Hence coordinate of m2 are

E = 2676841.494m

N = 3301704.368m

Conclusion:

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Hence the independent co- ordinates of minor station m2 were calculated adopting

the principles of Resection .

B) Intersection

Intersection is the procedure of determining the position of the unknown points

with the help two known points. Intersection is done by taking angular measurements

from the known point to the unknown points. The distances between the known and

unknown points are measured by solving the triangle by using sine law and the triangle

should be well conditioned as non of the angles should be less than 30 ° and not more than

90°.

In our camp , we have to find out the height of coordinates of the water tower.

m2 H1 TOWER

d

H2

M11

A6M1

α 1= 149°14’15"

α 2= 25°57’10"

x = 4°48’35"

Using sin law in ∆ABC,

sin<xd

=sin<α 1H 1

= sin<α 2H 2

Now,

H2=227.100m

H1 =237.091m

Bearing of m2M11 = 235°19’ 20"

Bearing of M11m2 = 55°19’ 20"

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Bearing of m2T = Bearing of m2M1-α 1 = 86°5’ 6"

Bearing of M11T = Bearing of M11m2 + α 2 = 81°16’ 31"

From m2T,From m2T,

Y =M2T cos(br. of m2T)=16.188mY =M2T cos(br. of m2T)=16.188m

X =M2T sin(br. of m2T)=236.538mX =M2T sin(br. of m2T)=236.538m

Thus the coordinates of the Tower are

E = 3301720.428 m

N =2677078.175 m

From M11T,

Y =M11T cos(br. of M1T)=42.034m

X =M11T sin(br. of M1T)=272.893m

Thus the coordinates of the Tower are

E = 3301720.543 m

N =2677078.353 m

From inst. St at m2,

H=237.091m

RL=1343.219m

HI=1.34m

Θ == 90°- 81°41’ 20"= 8°18’ 40"

RL of T = RL+HI+H tan <θ

= 1379.214m

From inst. St at m2,

H=277.100m

RL= 1342.476m

HI=1.36m

Θ = 277°16’ 50"- 270°= 8°18’ 40"

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RL of T = RL+HI+H tan <θ

= 1379.237m

Height of tower is= (1379.237+1379.214)/2 =1379.226m

II.6.0 COMMENTS AND CONCLUSION:

The Site for the survey camping was the NEA Training Center. The topographic

map of given area was prepared as per the given norms and specification.

The project of topographical survey was felt very effective and we felt as if we were

appointed as an engineer and working as per the norms and specification provided.

Further it is very interesting while using Total station. In this modern age of surveying,

Theodolite seems to be ineffective in comparison to the Total station. After the traverse

was plotted in grid sheet we used plane tabling method to check whether our calculation

and plotting was correct or not. Finally checks were successful and we got it right.

We were able to familiarize ourselves with the different practical approaches applied in

surveying in the actual field condition. We experienced the difference between working

in a smaller area and working in a larger area. Along with gaining a lot of confidence

regarding the use of the instruments, we also felt the responsibility of planning, executing,

and completing a project. As a whole, we understood the value of teamwork and mutual

coordination in the execution of any project. Completion of survey work within the period

and under the required precision was one of the major tasks that we had achieved during

the camp.

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CHAPTER 3

3.0 TOTAL STATION:

3.1 INTRODUCTION:

A total station is an optical instrument used a lot in modern surveying and

archaeology and, in a minor way, as well as by police, crime scene investigators, private

accident re-constructionists and insurance companies to take measurements of scenes. It

is a combination of an electronic theodolite (transit), an electronic distance meter (EDM)

and software running on an external computer known as a data collector

With a total station one may determine angles and distances from the instrument

to points to be surveyed. With the aid of trigonometry and triangulation, the angles and

distances may be used to calculate the coordinates of actual positions (X, Y, and Z or

northing, easting and elevation) of surveyed points, or the position of the instrument from

known points, in absolute terms.

Some total stations also have a GPS interface which combines these two

technologies to make use of the advantages of both (GPS - line of sight not required

between measured points; Traditional Total Station - high precision measurement

especially in the vertical axis compared with GPS) and reduce the consequences of each

technology's disadvantages (GPS - poor accuracy in the vertical axis and lower accuracy

without long occupation periods; Total Station - requires line of sight observations and

must be set up over a known point or within line of sight of 2 or more known points).

Most modern total station instruments measure angles by means of electro-optical

scanning of extremely precise digital bar-codes etched on rotating glass cylinders or discs

within the instrument. The best quality total stations are capable of measuring angles

down to 0.5 arc-second. Inexpensive "construction grade" total stations can generally

measure angles to 5 or 10 arc-seconds.

Measurement of distance is accomplished with a modulated microwave or infrared

carrier signal, generated by a small solid-state emitter within the instrument's optical path,

and bounced off of the object to be measured. The modulation pattern in the returning

signal is read and interpreted by the onboard computer in the total station. The distance is

determined by emitting and receiving multiple frequencies, and determining the integer

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number of wavelengths to the target for each frequency. Most total stations use a purpose-

built glass Porro prism as the reflector for the EDM signal, and can measure distances out

to a few kilometers, but some instruments are "reflectorless", and can measure distances

to any object that is reasonably light in color, out to a few hundred meters. The typical

Total Station EDM can measure distances accurate to about 3 millimeters or 1/100th of a

foot.

Some modern total stations are 'robotic' allowing the operator to control the

instrument from a distance via remote control. This eliminates the need for an assistant

staff member to hold the reflector prism over the point to be measured. The operator

holds the reflector him/herself and controls the total station instrument from the observed

point.

The basic principle of Total Station is that the distance between any two points

can be known once the time light takes to travel the distance and back and the velocity of

light is known. Then the following relation, which is already programmed in the memory

of the instrument along with other correction factors, calculates the required horizontal

distance and is displayed on the LCD screen.

SETUP:

1. Place tripod approximately over a known point locking legs at a convenient height

so machine will be at or lower than eye level and the legs are at equal distances

from each other. Eyeball the head of the tripod so it is as close to level as possible.

Be sure the legs of the tripod are firmly planted into the ground.

For smooth surfaces (such as concrete, asphalt, or tile), use folding metal

tripod footing to secure the legs.

2. Remove instrument carefully from casing with both hands. Place on top

(supporting with top handle) of tripod and tighten centering screw below platform

into instrument, aligning the three corners of machine and platform. Use sight

tangent screw on back side of LCD display to center the instrument over the exact

known point to be surveyed.

3.2 POWER AND PREPARATION

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a. Attach one of the batteries to the side of instrument with the clamp side up. Press

any one of the five buttons below the display to turn on machine. It shall beep and

the display should indicate the instrument is not level and must be leveled and

indexed (precisely level internal components).

To switch power off, hold ESC button and press indicated button that

corresponds to OFF on the display.

If the battery is at a low level, the following will be displayed, “Battery is

low!”-switch batteries and charge the drained one using provided jack.

Prior to storing the instrument for its next use, check the status of both

provided batteries. If either is only ENTIRELY drained, charge overnight

using given equipment.

b. Locate the horizontal level bubble above the LCD display. Rotate instrument by

loosening the horizontal clamp and align the display with any two of the leveling

screws. Tighten or loosen the left screw so bubble is in center. Rotate instrument

clockwise to the next two screws and again use the left one to center bubble.

Rotate to the final two pair of screws and center bubble. Check stationary leveling

bubble to see if it is center. If not, repeat previous leveling process.

If the error message “Tilt out of range” is displayed, it is indicating the

instrument is off-level. Relevel the instrument.

c. To index the vertical circles, loosen the vertical clamp, and manually rotate the

telescope either way twice. The beep should be heard and the zenith angle (ZA

vertical angle) will appear on the LCD display.

d. Loosen the horizontal clamp and rotate the instrument clockwise twice to index

the horizontal circles. The beep is heard again and the horizontal angle (HAR) is

displayed.

Vertical and horizontal indexing has now been completed.

e. Note the menus displayed. Each option shown on the home page (reached by

pressing ESC) opens a section which contains several (up to 3) pages. To scroll

through these pages to reach other options, press button left of the yellow ESC

button that reads PX.

21

f. Set the target and instrument height by pressing Ht. in S-O mode. Measure the

target height by reading the measurement on the reflector pole at the clamp (set at

any arbitrary height suitable for job). Measure the instrument height by taping the

distance from the black point on side of instrument (level with center of telescope)

to the known point on ground.

Be sure to note the units used (currently default set at feet and decimal

fractions of feet; see manual to change to metric units) and height of

instrument and target in the field book.

When using two reflecting poles, be sure to set each at same height.

3.3 ANGLE MEASUREMENT:

1. Sight the first point (focus with eye piece and align center hairs with center of

reflector) using the horizontal clamp and the fine motion screw. Set the angle to

zero by pressing 0SET in THEO mode. Sight the second target and read the HAR

on the display.

If you wish to read the angle by rotating the instrument to the left, press

R/L in THEO mode (display will read HAL or HAR for left or right

respectively).

2. For higher accuracy, the average of a number of readings can be taken using

repetition. Sight the first target and press REP in THEO mode. Press BS (back

sight) then sight the second target. Press FS (fore sight) and the angle between the

two will be displayed. Sight the first target again, presses BS, and site the second

target again and press FS. The average of the two readings will be displayed.

Repeat up to 10 times for higher accuracy.

3. The slope of the line being shot can be displayed as a percentage by pressing ZA

% in THEO mode. This is read as VA and gives the percentage grade of the line.

Press it again to return to the ZA reading.VA% will be displayed when the

parameter is set to “Horizontal 0” instead of “Zenith 0” but performs the same

function.

22

Fig:Total Station

3.4 DISTANCE AND ANGLE MEASUREMENT:

This is the most useful and suggested method. The working procedure is described

as follow:

1. Sight target and select for slope, horizontal, or height (SHV) measurement. Press

Sdistto start the measurement and STOPto end. The distance, vertical, and

horizontal angle are displayed. Press SHVto view the other measurements

(Horizontal distance or Height difference).

23

2. To measure the horizontal distance several times and display the average, sight the

target and press H-distin THEOmode. Three measurements are taken and the

average (H-A) is displayed after a few seconds.

* The most recently taken data can be recalled and displayed by pressing

RCLin the EDM mode.

3.5 COORDINATE MEASUREMENT:

This is not much more useful. So co-ordinate measurement is not suggested for

use.

1. In order to begin the coordinate measure, set the initial coordinates of the station.

This is done by pressing the S-O button at the main menu. Then press the Stn-P

button on the second page of the S-O menu. Choose the Input button, then set the

initial coordinates and press ENTER.

2. Sight the target and press COORD in S-O mode, then press STOP to end the

measurement. The coordinates of the target are given with respect to the initial

starting position (0,0,0) and designated direction to be North.

3.6 MEASURING THE DISTANCE BETWEEN 2 POINTS:

1. Sight the first position and press either Sdist, Hdist, or Vdistin EDM mode to start

the measurement. Stop the measurement by pressing the STOP and sight the next

point. Press MLM on the same page to start the measurement, the press STOP to

stop the measurement. The slope, horizontal, and height difference between the

two points is displayed. This can be repeated as many times as necessary.

2. The slope may be read as a percentage by pressing S% in the same mode after the

missing line measurement has finished. This displays the percent grade between

the two points.

3.7 DISTANCE SETTING-OUT MEASUREMENT:

1. To find the direction and distance of a point set out a wanted distance from the

instrument station, sight the reference direction and press 0SET in THEO mode to

set the HAR at 0. Turn theodolite until the required angle is displayed and locks

the horizontal movement.

24

2. Press ESC to go to basic mode and go to S-O mode. Go to S-O_D for the data and

input the desired distance to set out. Set the reflecting prism in the sighting line

and press SO_Hdto start the distance measurement. The difference between the

desired distance and the measured distance is displayed on the 1st line.

3. Move the reflecting prism towards or away from the Instrument until H distance

becomes 0m to determine the point at the desired distance.

* If there is negative (-) data: Move prism away from Instr.

* If positive (+) data: Move prism towards Instr.

* Press STOP to end the measurement.

3.8 COORDINATES SETTING-OUT MEASUREMENT:

a. Set the station coordinates and initial azimuth angle. Press S-O_P in S-O mode

and input the desired coordinates for N and E and press YES to store the data.

Press SO_HA in S-O mode to start the angle measurement. The setting-out

horizontal angle, HA is displayed. Use the horizontal clamp and fine motion screw

to turn theodolite until HA reads 0° 00’ 00” and lock the clamp.

b. Sight the reflecting prism on the sighting line and press SO_HD and move

reflecting prism until H reads 0m as in part 3 of the distance setting-out

measurement.

3.9 LEVELLING

Leveling is a branch of surveying, the objectives of which are:

To find the elevation of given points with respect to a given or assumed

datum.

To establish points at a given elevation or at different elevations with respects

to a given or assumed datum.

Two types of leveling are used in general Engineering practices, namely direct

leveling (spirit leveling) and in-direct leveling (trigonometric leveling).

DIRECT LEVELLING:

25

It is the branch of leveling in which the vertical distances with respect to a

horizontal line (perpendicular to the direction of gravity) may be used to determine the

relative difference in elevation between two adjacent points. A level provides horizontal

line of sight, i.e. a line tangential to a level surface at the point where the instrument

stands. The difference in elevation between two points is the vertical distance between

two level lines. With a level set up at any place, the difference in elevation between any

two points within proper lengths of sight is given by the difference between the staff

readings taken on these points. By a succession of instrument stations and related

readings, the difference in elevation between widely separated points is thus obtained.

Following are some special methods of direct (spirit) leveling:

DIFFERENTIAL LEVELING:

It is the method of direct leveling the objective of which is solely to determine the

difference in elevation of two points regardless of the horizontal positions of the points

with respect of each other. This type of leveling is also known as fly leveling.

PROFILE LEVELING:

It is the method of direct leveling the objective of which is to determine the

elevations of points at measured intervals along a given line in order to obtain a profile of

the surface along that line.

CROSS SECTIONING:

Cross-sectioning or cross leveling is the process of taking levels on each side of main line

at right angles to that line, in order to determine a vertical cross-section of the surface of

the ground, or of underlying strata, or of both.

At every 20m chainage the readings were taken for cross sectioning. The RL were taken

where the change in slope was noticed or remarkable points were noticed or else at 5m

and 10m both left and right. Autolevel was used for this purpose. Cross sectioning was

plotted on the graph.

RECIPROCAL LEVELING:

Reciprocal leveling

26

1For transferring the RL across the bridge reciprocal leveling was performed. This

method eliminates the error due to focusing, collimation, earth’s curvature and refraction

of atmosphere etc.

True difference in elevation between A and B = H = ha- (hb-e)

Also the true difference in elevation = H = (ha '- e)-hb’

Taking the average of the two differences we get the difference in elevation between A

and B.

.

INDIRECT LEVELING:

Indirect method or trigonometric leveling is the process of leveling in which the

elevations of points are computed from the vertical angles and horizontal distances

measured in the field, just as the length of any side in any triangle can be computed from

proper trigonometric relations.

The first operation is required to enable the works to be designed while the second

operation is required in the setting out of all kinds of engineering works. Leveling deals

with measurements in a vertical plane.

TEMPORARY ADJUSTMENT OF LEVEL: The temporary adjustment for a level

consists of the following:

Setting up the level: The operation of setting up includes fixing the instrument on

the stand and leveling the instrument approximately.

27

)]''()[(2

1baba hhhhH

Levelingup: Accurate leveling is done with the help of foot screws and with

reference to the plate levels. The purpose of leveling is to make the vertical axis

truly vertical and horizontal line of sight truly horizontal.

Removal of parallax: Parallax is a condition when the image formed by the

objective is not in the plane of the cross hairs. Parallax is eliminated by focusing

the eyepiece for distinct vision of the cross hairs and by focusing the objective to

bring the image of the object in the plane of cross hairs.

PERMANENT ADJUSTMENTS OF

LEVEL:

To check for the permanent adjustments

of level two-peg test method should be

performed. Two staffs were placed at A and B

of known length (about 60 m). First the

instrument was setup on the line near B and

both staff readings (Top, Middle, and Bottom)

were taken. Then, the instrument was setup at

the middle C on the line and again both staff

readings on A and B was taken. Then

computation was done in order to check whether

the adjustment was within the required accuracy

or not.

The error obtained was within the given

permissible error. So, the permanent adjustment

was not required.

Inst. Set UpObject Station

Staff Reading in meter Mean(H) =(T+M+B)/

3

Mean-M

(<1mm)Top (T)

Mid (M)

Bottom (B)

Mid of A and B A 1.290 1.165 1.040 1.165  B 1.357 1.229 1.103 1.22966667  

Near AA 1.302 1.297 1.293 1.29733333  B 1.623 1.360 1.101 1.36133333  

True level difference between A and B = Ha-Hb = ∆h1 = 0.06466667

Apparent level difference between A and B = Ha'-Hb' = ∆h2 =0.064

Collimation Error = ∆h1-∆h2 =0.00067

28

Horizontal distance between pegs A & B (H) = 50 m

Precision = e/H =1: 71428.57143

BOOKING AND REDUCING LEVELS:

There are two methods of booking and reducing the elevation of points from the

observed staff reading:

Height of the Instrument method

Arithmetic Check: ∑BS – ∑F.S. = Last R.L. – First R.L.

Rise and Fall method

Arithmetic Check: ∑ BS – ∑ F.S. = ∑ Rise – ∑fall = Last R.L. – First R.L.

FLY LEVELING:

The RL of Given TBM1 point was found by transferring the level from Known

BM.In this method auto level was used and the level was transferred directly by taking

BS and FS at every Turning Point.

For transferring the RL across the bridge reciprocal leveling was performed. This method

eliminates the error due to focusing, collimation, earth’s curvature and refraction of

atmosphere etc.

True difference in elevation between A and B = H = ha- (hb-e)

Also the true difference in elevation = H = (ha '- e)-hb’

Taking the average of the two differences we get the difference in elevation between A

and B.

LEVEL TRANSFER TO MAJOR AND MINOR TRAVERSE STATIONS:

The R. L of the temporary benchmark was then transferred to the control stations

29

)]''()[(2

1baba hhhhH

of the major and minor traverse. The closing error was found to be within the permissible

limits. The misclosure was adjusted in each leg of the leveling path by using the

following formula:

Permissible error = ±25K mm.

Where k is perimeter in Km

Actual Error (e) = ∑BS – ∑F.S. = Last R.L. – First R.L.

Correction ith leg=-(e x (L1 + L2 +….+ Li)/P

Where L1, L2… Liare Length of 1st2nd,..ith leg.

P is perimeter

Relative Precision= 1/(p/e)

3.10 DETAILING

3.10.1 TACHEOMETRY:

Tachometry is a branch of angular surveying in which the horizontal and vertical

distances of points are obtained by optical means. Though it has less accuracy, about

1/300 to 1/500, it is faster and convenient than the measurements by tape or chain. It is

very suitable for steep or broken ground, deep ravines, and stretches of water or swamp

where taping is impossible.

The objective of the tachometric survey is the preparation of the topographic map

or plan with both horizontal and vertical controls. For the survey of high accuracy, it

provides a check on the distances measured by tape.

The formula for the horizontal distance, for the tachometer with the additive constant

0.00 and multiplying constant 100.00 is,

H= K S Cos2Ө

The formula for the vertical distance is,

V = (K S Sin2Ө)/2 = HTanӨ

Where, S = staff intercept =Top Reading – Bottom Reading

K = Multiplying Constant (Generally = 100)

Ө = Vertical angle on Theodolite.

30

Thus knowing the V value, reduced level (R. L.) of instrument station, Height of

instrument (H. I.) and central wire reading (R) the R. L. of any point under observation

can be calculated as:

R. L. of Point = R. L. of Instrument Station + H. I. + V- R

3.10.2 CONTOURING:

A contour is an imaginary line, which passes through the points of equal

elevation. It is a line in which the surface of ground is intersected by a level surface.

Every fifth contour lines must be made darken. While drawing the contour lines, the

characteristics of the contours should be approached.

The characteristics are as follows:

Two contours of different elevations do not cross each other except in the case of

an overhanging cliff.

Contours of different elevations do not unite to form one contour except in the

case of a vertical cliff.

Contours drawn closer depict a steep slope and if drawn apart, represent a gentle

slope.

Contours equally spaced depict a uniform slope. When contours are parallel,

equidistant and straight, these represent an inclined plane surface.

Contour at any point is perpendicular to the line of the steepest slope at the point.

A contour line must close itself but need not be necessarily within the limits of the

map itself.

A set ring contours with higher values inside depict a hill whereas a set of ring

contours with lower values inside depict a pond or a depression without an outlet.

When contours cross a ridge or V-shaped valley, they form sharp V-shapes across

them. Contours represent a ridgeline, if the concavity of higher value contour lies

towards the next lower value contour and on the other hand these represent a

valley if the concavity of the lower value contour, lies toward the higher value

contours.

31

The same contour must appear on both the sides of a ridge or a valley.

Contours do not have sharp turnings.

3.11 METHODS OF CONTOURING:

Taking the reading at the change point on the ground does the indirect method of

locating contours. The interpolation method is used to draw the contour lines.

Interpolation of contours is done by estimation, by arithmetic calculations or by graphical

method. The eye estimation method is extremely rough and is used for small-scale work

only.

There are two method of locating contour:

i) The Direct Method:

In this method, the points of equal elevations are found directly on the field. The

horizontal control of the point is found by the help of plane table.

ii) The Indirect Method:

In this method, some suitable guide points need not necessarily be on the contour.

There are some of the indirect methods of location the ground points:

a) Square Method

b) Cross- Section Method

c) Tachometric Method

Interpolation is the process of spacing the contours proportionately between the

slopes of the ground between the two points is uniform. The interpolation of contour cans

be done on following three ways:

1) ESTIMATION:

2) ARITHMETIC CALCULATION:

Generally, arithmetic calculation method of interpolation is used to draw the

contour lines and is performed as follows:

Dist .of ContourPo

int=(Diff .inRL .of OnePt . _&_Reqd .Pt .)∗(Hz .Dist .inScale )

Difference inRL .of TwoKnown

Pts

.

3) GRAPHICAL METHOD:

32

Generally, we use arithmetic method of interpolation to draw the contour line.

3.11 COMPUTATION AND PLOTTING

For the calculations as well as plotting, we applied the coordinate method (latitude

and departure method). In this method, two terms latitude and departure are used for

calculation. Latitude of a survey line may be defined as its coordinate lengths measured

parallel to an assumed meridian direction. The latitude (L) of a line is positive when

measured towards north, and termed Northing and it is negative when measured towards

south, and termed Southing. The departure (D) of a line is positive when measured

towards east, and termed Easting and it is negative when measured towards south, and

termed Westing. The latitude and departures of each control station can be calculated

using the relation:

Latitude = L Cos

Departure = L Sin

Where, L=distance of the traverse legs

=Reduced bearing

If a closed traverse is plotted according to the field measurements, the end of the

traverse will not coincide exactly with the starting point. Such and error is known as

closing error.

Mathematically,

Closing error (e) = √ {(L) 2 + (D) 2}

Direction, tan θ = D/L

The sign of L and D will thus define the quadrant in which the closing error lies.

The relative error of closure = Error of Closure / Perimeter of the traverse

= e / p= 1 / (p / e)

The error (e) in a closed traverse due to bearing may be determined by comparing

the two bearings of the last line as observed at the first and last stations of traverse. If the

closed traverse, has N number of sides then,

Correction for the first line = e/N

Correction for the second line = 2e/N

33

And similarly, correction for the last line = Ne/N = e

In a closed traverse, by geometry, the sum of the interior angles should be equal to

(2n-4) x 90˚ where n is the number of traverse sides. If the angles are measured with the

same degree of precision, the error in the sum of the angles may be distributed equally

among each angle of the traverse.

The Bowditch’s method or the compass rule is mostly used to balance a traverse

where linear and angular measurements are of equal precision. The total error in latitude

and in the departure is distributed in proportion to the lengths of the sides.

Mathematically,

Correction in departure of a side of traverse

= (Total Dept. Misclosure / Traverse Perimeter)*(length of that side)

Correction in latitude of a side of traverse

= (Total Lat. Misclosure / Traverse Perimeter) * (length of that side)

In order to measure the lengths of the sides of the traverse, two ways taping

(forward and backward) is done. In difficult areas where taping is not possible, other

methods like the subtense bar is used. The difference in values obtained by forward and

backward taping is called discrepancy. In addition, the reciprocal of the discrepancy

divided by the mean of the two measurements is called precision. Both the discrepancy

and the precision for each traverse leg should be within the given limits.

Mathematically, Discrepancy = | Forward length - Backward length |

And Linear precision = 1 / (Mean length / Discrepancy)

The coordinates of traverse station were found out by resection. The resection point was

selected at the top of hostel building from where all the known points can be sighted. The

coordinates of known points are given below.

PLOTTING OF MAJOR & MINOR TRAVERSE :

The traverse was made closed in order to check the sum of interior angles, which

should be equal to (2n-4)*90 degrees, where n= number of control points. (Traverse

stations or legs).

The bearing of the one of the stations with another adjacent station was found out

compass. The bearing of other traverse legs were obtained from the help of bearing of

34

preceding line and the included angle at the particular station.

After computing the co-ordinate of each of the control points, they were made

ready to plot in grid paper. Both major and minor traverses were plotted to 1:1000 scales.

The plotted traverse was made at the center of the sheet with the help of least co-ordinates

and highest co-ordinates.

3.12 COMMENTS AND CONCLUSION

The site for survey camping was NEA Training Center. The pattern was very

suitable because all the facilities for engineering work were available with the good

environment of doing work.The arrangements of the survey instruments were appreciable

although there were some faulty instruments that made the fieldwork time consuming.

Some instruments like theodolite, levels etc. do not given the accurate reading. Some

other problems during the field works were during fly leveling during transferring the

R.L. from given benchmark to the CP due to the by traffics disturbances.

The given Topography survey camp work was finished within the given span of

time. The subject survey needs practice as much as possible. For surveying, theory can

only taken as the introduction but if there is practice, there will be much gain of

knowledge about the techniques of surveying. Thus, this camp helps us by practicing the

survey work to gain the much essential knowledge as far as possible. It is better to say

that it provides us a confidence to perform survey and apply the techniques at any type of

problem facing during the actual work in the future career.The whole area of NEA

Training Center was divided in number of plots. A single group had to complete a single

plot following the routine provided. Then from the control stations details were taken by

tachometry. Recorded data's were established by MS-excel and the drawing was prepared.

After computing the co-ordinate of each of the control points, they were plotted in grid

paper. Both major and minor traverse were plotted to 1:1000 and 1:500 scale respectively.

The plotted traverse was made at the center of the sheet with the help of least co-ordinates

and highest co-ordinates. Contouring was done with the help of arithmetic interpolation.

35

CHAPTER 4

4.0 BRIDGE SITE SURVEY

4.1 INTRODUCTION

This part of the Survey Camp deal with the bridge site survey at Dolalghat where a

narrow river flowed. The structures that are constructed with the objective of connecting

two places separated by deep valleys or gorges or rivers and streams are basically known

as BRIDGES. The bridges are usually a part of roads making the roads shorter and hence

economical. In countries like Nepal, where there are a lot of uneven lands and plenty of

rivers, bridges are the most economic and efficient ways to join two places by road in a

convenient way. The bridge site surveying was conducted in a Dolalghat.

4.2. OBJECTIVES :

Following are the objectives of Bridge site survey:

To select the best location in terms of convenience, economy and geological stability.

To calculate the length of the bridge axis via triangulation.

To take sufficient data of the details including the spot heights, around the bridge in

order to prepare a topographical map of the area, cross section of the river at certain

intervals and longitudinal section of the river.

4.3 BRIEF DESCRIPTION OF THE AREA

Bridge site survey was done over cha khola river. The site is surrounded with

stepped grassy fields. Its flow direction is north to south. There is plain ground as well as

highly sloping ground on some places surrounding. There is big and small stones on the

river.

4.3.1 HYDROLOGY, GEOLOGY AND SOIL

In both sides of the river there was steep slope that was the main obstacle. The

river was seasonal where water flow in high speed during rainy season and less at dry

season.

36

4.4 NORMS (TECHNICAL SPECIFICATIONS)

The following norms were followed while performing the bridge site survey:

Determining the length of the bridge axis and control point fixing was done by the

method of triangulation. While forming triangles one of the angles of the triangles

were greater than 120o or less than 30o.

The triangulation angle was measured on two sets of readings by theodolite and the

difference between the mean angles of two sets of readings had to be within 1’.

Transferring the level from one bank to another bank had to be done by the method

of reciprocal leveling.

The scale for plotting of our topographical map is 1:500.

In order to plot the longitudinal section of the river, data had to be taken along the

river bed upto150 m upstream and at least 75 m downstream. However it was not

possible in our case.

The plot for the longitudinal section along the flow line was done in a scale of 1:50

for vertical and 1:500 for horizontal.

For the cross section profile, data had to be taken at 10 m intervals both upstream

and downstream, and one at the bridge axis.

4.5 EQUIPMENTS USED

Total station

Tapes

Auto Level

Compass

Hammer

Pegs

Tripod

37

4.6 METHODOLOGY :

The various methods were performed during the bridge site survey such as

triangulation, leveling, Tachometry, cross section, L-section etc. The brief descriptions of

these methodologies are given below

4.6.1RECONNAISSANCE

For the purpose of the shortest span, the stations were set perpendicular to the

flow direction. The riverbanks were not eroded and were suitable for bridge construction.

The chance of change of direction of river on the selected axis line was nominal.

4.6.2 SITE SELECTION:

The sites was chosen such that it should be laid on the very stable rocks or hill

slope at the bed of river as far as possible and not affect the ecological balance of the flora

and fauna of the site area. The bridge axis should be so located such that it should be

fairly perpendicular to the flow direction and at the same time, the river width should be

narrow from the economical point of view and the free board should be at least 5m. The

starting point of bridge axis should not in any way lie or touch the curve of the road.

4.6.3 TRIANGULATION

For the determination of the approximate span of the bridge axis Triangulation

was performed. The triangulation stations were taken as the control points for detailing.

Following criteria is met in this process:

Two points on either bank of the river were fixed as control points and one of the

sides of the triangle was taken as the bridge axis.

The base line was measured accurately measured by two-way tapping and interior

angles were measured by taking two sets of reading by theodolite.

The accurate span of bridge was computed by applying sine rule.

To minimize the plotting error well-conditioned triangles were constructed i.e. the

angles greater than 30 degree, less then 120 degrees and nearer to 60 degree. The

best triangle is equilateral triangle.

38

Fig: Bridge Triangulation

4.7 TOPOGRAPHIC SURVEY

A total of 4 control stations were selected along the banks. Thus a traverse was

formed running across the river, covering a distance of 150m upstream and 75 m

downstream.

The method of triangulation was used for the determination of the bridge axis as

well as the traverse legs, which also served as checks on our work.

And the triangulation angles with two sets of reading were taken using a

theodolite. Details of the objects around the bridge along with their spot heights

were taken from these control stations by tachometric method.

While transferring the R.L. from the given benchmark to the control stations, fly

leveling was done. And for transferring the R.L. from one point to another point

across the bridge axis, reciprocal leveling was done.

All the internal angles were measured using Totalstation. Then Sine Law was used

to calculate the lengths of the other legs of the triangulation series along with the

proposed bridge axis.

4.8 LONGITUDINAL SECTION (L-SECTION)

The L-Section of the river is required to give an idea about the bed slope, nature

of the riverbed, and the variation in the elevations of the different points along the length

of the river. Keeping the instrument at the control (triangulation) stations on the river

banks, the different detailing points along the center line of the river at an interval of

about 10m up-to a 150m upstream and 75 m downstream is taken.

The R.L.s of the traverse stations being known previously by reciprocal leveling; the

levels of the different points on the river were calculated.

39

A

BC

D

4.9 CROSS SECTION

Cross sectioning of river at a point extends laterally on either side of the center line of the

river at right angle to the L-section.

At every 10m chainage the readings were taken for cross sectioning. The reading were

taken where the change in slope was noticed or remarkable points were noticed or at 10m

interval. Totalstation was used for this purpose.

Cross sectioning was plotted on the graph at a scale of 1:100vertically and 1:100

horizontally

4.10 LEVELING

Transferring R.L. from B.M. to control points:

The R.L of benchmark BM = 622.00 m was given and was transferred to the triangular

stations from the B.M. by fly leveling along the road turning points by taking the back

sight reading to the bench mark which should be within the given accuracy. Reciprocal

leveling transferred the R.L. to the opposite bank of the river.

RECIPROCAL LEVELING:

For transferring the RL across the bridge reciprocal leveling was performed. This method

eliminates the error due to focusing, collimation, earth’s curvature and refraction of

atmosphere etc.

40

True difference in elevation between A and B = H = ha- (hb-e)

Also the true difference in elevation = H = (ha '- e)-hb'

Taking the average of the two differences we get the difference in elevation between A

and B is given by H=1/2[(ha-hb) + (ha’-hb’)]

4.13 COMMENTS AND CONCLUSION :

The bridge site survey was performed to gain idea for selecting the bridge axis.

Triangulation was performed to get the length of the proposed bridge. Similarly, the

cross-section and longitudinal section were performed. The X-section was performed at

the interval of 10m. The longitudinal section was about 150m upstream and 75m

downstream. In addition, details were taken from the respective stations. The cross-

section was taken at the banks of river and at the middle of the river to get the profile of

the flowing river. In addition, we marked the high flood level and low flood level.

Similarly, we transferred the reduced levels of the stations from the known benchmark.

41

CHAPTER 5

5.0 ROAD ALIGNMENT SURVEY AND GEOMETRIC DESIGN

5.1 INTRODUCTION

Roads are specially prepared ways between different places for the use of

vehicles, people and animals. It is an accepted fact that of all the mode of transportation,

road transport is the nearest to the people. The passengers and the goods have to be first

transported by road before reaching a railway station or a port or an airport. The road

network alone could serve the remotest villages of the vast country like ours. In countries

like Nepal, where there are less chances of airways and almost negligible chances of

waterway, roads form a major part of the transportation system. Therefore, it would not

be an exaggeration in saying that the roads have an utmost importance.

This part of the survey Camp dealt with road alignment survey done at in Nepal

Electricity Authority Training Center, Kharitapi. The duration of the survey was two

days.

5.2 OBJECTIVES

Road Alignment Survey was done to accomplish the following objectives:

To choose the best possible route for the road such that there were a minimum number of

Intersection Points (I.P.) thereby decreasing the number of turns on the road.

To design smooth horizontal curves at points where the road changed its direction, in

order to make the road comfortable for the passengers and the vehicles traveling on it.

To take sufficient data of the details including the spot heights, around the road segment

in order to prepare a topographical map of the area, cross section of the road at certain

intervals and longitudinal section of the road segment, hence making it convenient to

determine the amount of cut and fill required for the construction of the road.

5.3 TOPOGRAPHYAND GEOLOGY OF THE AREA

The starting point of the route was the CP1 major station. The site is surrounded

with various type of ground features with grass in most of the part. The route selected by

our group B3 with 11 I.P. and minimum grade of 0.1%and maximum grade of 7%. There

are several rise and fall along the route needing lots of cutting, and filling.

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The road alignment survey was done at Nepal Electricity Authority Training Centre

Bhaktapur. The area was having steep slopes as well as plane land. The area was ideal for

survey for hill road. Steep slopes and drastic change in alignment made the work more

challenging and more interesting. The area was full of clay and exposed rocks particularly

of metamorphic type. The area having steep slopes, but few slopes were unstable and

there was chance of slide, so slope protective works are necessary.

5.3.1 HYDROLOGY AND GEOLOGY :

The road had to go along a damp route that was much undulated. The place was

damp and clayey. There were no large boulders or rocks of any kind along the proposed

site.

5.3.1.1SOIL :

When the soil surface is inclined, there is a component of gravity that tends to

move the soil downward. If along the potential slip surface in the soil the stress produced

by gravity exceeds the shear strength of the soil along the potential failure surface, the

slope will become unstable. Obviously, the shear strength of soil is largely depends upon

the type of soil. Cohesive soil has more shear strength than others do. The hard and dense

soil is best for slopes. Other kinds of soils were not found along our proposed route.

5.4 NORMS (TECHNICAL SPECIFICATIONS)

While performing the road alignment survey, the following norms were strictly

followed:

Simple horizontal curves had to be laid out where the road changed its direction,

determining and pegging three points on the curve - the beginning of the curve, the

middle point of the curve and the end point of the curve along the centerline of the road.

The radius of the curve had to be greater than 15m and

The gradient of the road had to be maintained below 7%

Cross sections had to be taken at 20 m intervals and also at the beginning, middle and end

of the curve, along the centerline of the road - observation being taken on either side of

the centerline.

Plan of the road had to be prepared on a scale of 1:500.

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L-Section of the road had to be plotted on a scale of 1:1000 horizontally and 1:100

vertically.

The cross section of the road had to be plotted on a scale of 1:100 (both vertical and

horizontal).

The amount of cutting and filling required for the road construction had to be determined

from the L-Section and the cross sections.

5.5 EQUIPMENTS USED

Theodolite

Staffs

Ranging rods

Tapes

Level

Compass

Hammer

Pegs

5.6 METHODOLOGY :

5.6.1 RECONNAISSANCE

The reconnaissance survey was carried out starting from the main road to the low

elevated region along the graveled road. Pegging was done at different places and the

possible I.P.s were also numbered and pegged. The condition of inter-visibility was

checked at each step.

5.6.2 HORIZONTAL ALIGNMENT

The locations of the simple horizontal curves were determined carefully considering

factors like the stability of the area, enough space for the turning radius, etc. The I.P.s was

fixed so that the gradient of the road at any place was less than 7%. After determining the

I.P.s for the road, theodolite was stationed at each I.P. and the deflection angles measured.

The distance between one I.P. and another was measured by two way taping.

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 MC

EC

O

BC

IP

The horizontal curves were set out by angular methods using theodolite at I.P. and tape.

Horizontal alignment is done for fixing the road direction in horizontal plane. For this, the

bearing of initial line connecting two initial stations was measured using compass. The

interior angles were observed using Theodolite at each IP and then deflection angles were

calculated.

Deflection angle = (360 or 180) - observed angle

Fig: Simple circular horizontal curve

Where,

BC: Beginning of curve

EC: End of curve

MC: Midpoint of curve

IP: Apex distance

If +ve, the survey line deflects right (clockwise) with the prolongation of preceding line

and deflects left if –ve (anti-clockwise). The radius was assumed according to the

deflection angle. Then the tangent length, EC, BC, apex distance along with their

chainage were found by using following formulae,

Tangent length (T L) = R x tan (/2)

Length of curve (L.C) = 3.142 x R x /180

Apex distance = R x 1/ (Cos (/2)-1)

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R

Tangent Length, BC1IP = R Tan /2

Apex distance, IPMC1= R(sec/2-1)

IPBC= IPEC: Tangent length

 : External deflection angle 

      R: Radius of curve

Chainage of BC = Chainage of IP – TL

Chainage of MC = Chainage of BC +LC/2

Chainage of EC = Chainage of MC + LC/2

The BC and EC points were located along the line by measuring the tangent

length from the apex and the points were marked distinctly. The radius was chosen such

that the tangent does not overlap. The apex was fixed at the length of apex distance from

IP along the line bisecting the interior angle.

After performing the necessary calculations, the points T1 and T2 were fixed at a distance

equal to the tangent length from I.P. using a tape. Then the line bisecting the internal

angle at the I.P. was found out with the help of a theodolite. And on this line, a peg was

driven at point M at a distance equal to the apex distance (VM) from the I.P. Then the

necessary calculations were done, thus giving the required numerical values of the

different parameters.

5.6.3 VERTICAL ALIGNMENT

Vertical profile of the Road alignment is known by the vertical alignment. In the

L-section of the Road alignment, vertical alignment was plotted with maximum gradient

of 12 %. According to Nepal Road Standard, Gradient of the Road cannot be taken more

than 12 %. In the vertical alignment, we set the vertical curve with proper design. Vertical

curve may be either summit curve or valley curve. While setting the vertical alignment, it

should keep in mind whether cutting and filling were balanced or not.

5.7 LEVELING

The method of fly leveling was applied in transferring the level from the given

B.M. to all the beginnings, mid points and ends of the curves as well as to the points

along the center line of the road where the cross sections were taken. After completing the

work of one way leveling on the entire length of the road, fly leveling was continued back

to the B.M. making a closed loop for check and adjustment. The difference in the R.L. of

the B.M. before and after forming the loops should be less than 25k mm, where k is the

total distance in km.

5.8 LONGITUDINAL SECTION

The L-Section of the road is required to give the road engineer an idea about the

nature of the ground and the variation in the elevations of the different points along the

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length of the road and also to determine the amount of cutting and filling required at the

road site for maintaining a gentle slope. In order to obtain the data for L-Section, staff

readings were taken at points at 20 m intervals along the centerline of the road with the

help of a level by the method of fly leveling. And thus after performing the necessary

calculations, the level was transferred to all those points with respect to the R.L. of the

given B.M. Then finally the L-Section of the road was plotted on a graph paper on a

vertical scale of 1:100 and a horizontal scale of 1:1000.

5.9 CROSS SECTION

Cross sections at different points are drawn perpendicular to the longitudinal

section of the road on either side of its centerline. Cross sections are also equally useful in

determining the amount of cut and fill required for the road construction. Cross sections

were taken at 5m intervals along the centerline of the road and also at points where there

was a sharp change in the elevation. While doing so, the horizontal distances of the

different points from the centerline were measured with the help of a tape as well as staff

and the vertical heights with a measuring staff. The R.L. was transferred to all the points

by performing the necessary calculations and finally, the cross sections at different

sections were plotted on a graph paper on a scale of 1:100 both vertical and horizontal.

5.10 CALCULATIONSAND PLOTTING

After the work of taking the data was completed, all the necessary calculations

were done and tabulated in systematic order. The calculations were done in order to

compute the Chainage of the different distinct points of the road using the following

relations:

Chainage of beginning of curve, BC1 = Chainage of I.P. - Tangent length

Chainage of mid point of curve, MC1 = Chainage of BC1 - 1/2* Curve length

Chainage of end of curve, EC2 = Chainage of BC1 - Curve length

Similarly,

Chainage of an I.P. = Chainage of previous I.P. + I.P. to I.P. distance.

The R.L. of the different points was also computed using this formula.

R.L. of a point = R.L. of station + Height of Instrument + H * Tan - Mid wire reading

Where, = Vertical Angle

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Hence, with the required calculated data regarding the road site in hand, the plan was

plotted on a scale of 1:500, L-Section on a graph paper on a scale of 1:1000 horizontal

and 1:100 vertical and the cross section at different points also on a graph paper on a

scale of 1:100 (both vertical and horizontal).

All the data, calculation (in a tabulated form) and the drawings of the necessary plan,

longitudinal section and the cross section of the road are attached with this report.

5.11 COMMENTSAND CONCLUSION

In spite of the different kinds of obstacles in the field, our group was successful in

completing the fieldwork as well as the office work in time. In the field, we had spent

quite some time discussing the route of the road and also in designing the curves, which

led to good results, The grade change was very sharp which created nuisance in working

with the Auto Level. However, all the group members were very cautious and tried their

best to get error free data and calculations. The road had to be designed on a sloping

ground, so our group members felt the restrictions during the cutting and filling.

Moreover, after performing this road alignment survey, we were able to build up our

confidence in designing roads at difficult terrain taking factors like economy,

convenience and its use into consideration.

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