KIIT POLYTECHNIC

Chapter-1

INTRODUCTION

1.1. SURVEYING-
Surveying is the art of determining the relative position of different objects on the surface of the earth by
means of measurements of distances, directions and elevations and then, preparing a map to any suitable scale.
TECHNICAL TERMS:
(i) Plan: A plan is a geographical representation of the features on the earth surface or below the earth
surface as projected on horizontal plane. This may not necessarily show its geographical position on
the globe. On a plan horizontal distances and directions are shown.
(ii) Map: The representation of earth surface on a small scale is called a map. The map must show its
geographical position on the globe.
(iii) Topographical map: The maps which are on sufficiently large scale to enable the individual features
shown on the map to be identified on the ground by their shapes and positions are called topographical
map.
(iv) Geographical map: The maps which are on such a small scale that the features shown on the map are
suitably generalized and the map gives a picture of the country as a whole and not a strict representation
of its individual features, are called geographical maps.

1.2. AIM AND OBJECTIVES OF SURVEYING-

The aim of surveying is to prepare a map to show the relative positions, horizontal distances, and elevation of
the objects on the surface of the earth. The map is drawn to some suitable scale. It shows the natural features of a
country, such as towns , villages , roads , railways , river etc. The objectives of surveying can be stated as follows.
(i) Collect and record data on the relative positions of points on the surface of the earth.
(ii) Compute areas and volumes using this data,required for various purposes.
(iii) Prepare the plans and maps required for various activities.
(iv) Lay out, using survey data, the various engineering works in correct positions.
(v) Check the accuracy of laid out lines, built of structure.

1.3 CLASIFICATION OF SURVAYING-

(1) PRIMARY CLASSIFICATION
3
 KIIT POLYTECHNIC

Surveying is primarily classified as:

(i) Plane surveying
(ii) Geodetic surveying

(i) PLANE SURVEYING:

In plane surveying the curvature of the earth is not taken into consideration. This is because
surveying is carried out over a small area so the surface of the earth is consider as plane .Plane surveying
is done on an area of less than 250 km2.
(ii) GEODETIC SURVEYING:
In geodetic surveying the curvature of the earth is taken into consideration. It is extended over
a large area. It is carried out over an area exceeding 250 km2.
(2) SECONDARY CLASSIFICATION
(i) Chain surveying
(ii) Compass surveying
(iii)Plane table surveying
(iv)Thedolite surveying
(v) Tachometric surveying
1.4 GENERAL PRINCIPLE OF SURVEYING-
The two basic principles of surveying need to be followed for accurately locating points on earth.
(i) To work from the whole to part:
The main principle of surveying is to work from whole to part whether it is plane or geodetic surveying.
To achieve this in actual practice, a sufficient number of primary control points are established with higher
precision in and around the area to be detail surveyed. Minor control points in between the primary control
points are then established with less precise method. Further details are surveyed with the help of these
minor control points by adopting any of the survey methods. The main idea of working from whole to part
is to prevent accumulation of errors and localize minor errors within the frame work of control points. On
the other hand if survey is carried out from part to whole, the errors would expand to greater magnitudes
and the scale of the survey will be distorted beyond control.
In general practice the area is divided into a number of large triangles and the positions of their vertices are
surveyed with greater accuracy, using sophisticated instruments. These triangles are further divided into
smaller triangles and their vertices surveyed with less accuracy.
(ii) To locate a new station by at least two measurements from fixed reference points / control points.
4
 KIIT POLYTECHNIC

The reference points / control points are selected in the area and distance between them, is measured
accurately. The line is then plotted to a convenient scale on a drawing sheet. In case, the control points are
co-ordinated, their locations may be plotted with the system of coordinates (Cartesian or spherical). The
location of the required point may then be plotted by making two measurements from the given control
points as explained below.

Let P and Q be two given control points. Any other point R can be located with reference to these points,
by any of the following methods.
P
P P P R

R
R R

Q
Q Q Q
(a) (b) (c) (d)
Fig.1
(i) By measuring distances PR and QR:- The distances PR and QR may be measured and the location
of R may be plotted by drawing arcs to the same scale to which line PQ has been drawn as shown
in Fig 1 (a).

(ii) By dropping a perpendicular from R on PQ:- A perpendicular RT may be dropped on the line PQ.
Distances PT, TQ and RT are measured and the location of R may be plotted by drawing the
perpendicular RT to the same scale to which line PQ has been drawn (Fig. 1 (b)).
The above two principles are generally used in “Chain surveying”.

(iii) By measuring the distance QR and angle PQR:- The distance QR and the angle PQR equal to α are
measured and location of R may be plotted either by means of a protractor or trigonometrically (Fig
1 (c)),
This principle is used in “Theodolite traversing”.

5
 KIIT POLYTECHNIC

(iv) By measuring the interior angles of the triangle PQR:- The interior angles P,Q and R of the triangle
PQR are measured with an angle measuring instrument such as theodolites. The length of sides PR
and QR are calculated by solving the triangle PQR and coordinates of R are calculated in the same
terms as those of P and Q. Even without calculating the co-ordinates, or sides the location of R can
be obtained by plotting the angles PQR and QPR (Fig 1(d).
This principle is used in the method of ‘Triangulation’.

Linear measurements

2.1 INTRODUCTION
There are two main methods of determining the distances between points on the surface of earth:
(i) Direct Measurement: In this method, distances are actually measured on the earth surface by means of
chains, tapes etc.
(ii) Computative Measurement: In this method distances are determined by calculation as in tachometry and
triangulation.

2.2 INSTRUMENTS FOR MEASURING DISTANCES

(i) Tapes
(ii) Steel Bands
(iii) Chains
(iv) Arrows
(v) Pegs
(vi) Ranging Rods

6
 KIIT POLYTECHNIC

(vii) Ranging Poles

(viii)Offset Rods

7
 KIIT POLYTECHNIC

(ix)Plumb Bobs

2.3 TAPES: Depending upon the material tapes are classified as

(i) Cloth or linen tape
(ii) Metallic tape
(iii)Steel tape
(iv)Invar tape
(i) Cloth or linen tape: Linen tapes are closely woven linen and varnished to resist moisture. They are
generally 10 metres to 30 metres in length and 12mm to 15 mm in width. Cloth tapes are generally used
for measuring offset measurements only due to following reasons :
(i) It is easily affected by moisture and shrunk.
(ii) Its length gets altered by stretching.
(iii) It is likely to twist and tangle.
(iv) It is not strong as a chain or steel tape.
(v) It is light and flexible and it does not remain straight in strong wind.
(vi) Due to continuous use, its figures get in-distinct.
(ii) Metallic Tape: A linen tape reinforced with brass or copper wires to prevent stretching or twisting of
fibers is called a metallic tape. As the wires are interwoven and the tape is varnished, these wires are
not visible to naked eyes. These tapes are available in different lengths but tapes of 20m and 30m lengths
are very common. These are supplied in leather case with winding machine. Each metre is divided into
decimeters and each decimeter is sub-divided into centimeters.
(iii) Steel Tape: Steel tapes are available with different accuracy of graduation. Steel tapes are available
in different lengths but 10m, 20m, 30m and 50m tapes are widely used in survey measurements. At the
end of the tape a brass ring is provided. The length of metal ring is included in the length of tape. A
steel tape of lowest degree of accuracy is generally superior to a metallic or cloth tape for linear
measurements.
(iv) Invar Tape: Invar tapes are made of an alloy of nickel (36%) and steel (64%) having very low co-
efficient of thermal expansion (0.000000122 per 1ºC). These are 6mm wide and are available in length
of 30m, 50m and 100m. These tapes are used for high degree of precision required for base
measurements.

2.4 Chains: The different types of chains are used in surveying and are given below.
8
 KIIT POLYTECHNIC

(1) Gunter’s chain: It is 66ft. long and divided into 100 links. Each link measures 0.66 ft.
(2) Engineer’s chain: It is 100ft. long and divided into 100 links. Each link measures 1 ft.

9
 KIIT POLYTECHNIC

Fig. 2.1
(3) Metric Chain: A metric chain is prepared with 100 or 150 pieces/ links of galvanized mild steel
wire of diameter 4mm. The ends of the pieces are bent to form loops and connected together by means of three
oval shaped rings which gives flexibility to the chain. Two brass handles are provided at the two ends of the
chain with swivel joints so that chain can be turned round without twisting. The outside of the handle is the
zero point or the end point of the chain. The length of the chain is measured from the outside of one handle to
the outside of the other. The length of a link is the distance between the centres of the two consecutive middle
rings as shown in the Fig. 2.1. The end links include the length of handle. Tallies are provided for marking
5m, 10m, etc are marked with letter “m” to distinguish the metric chain from non-metric chain. The length of
chain whether 20m 0r 30m is indicated on the handle for easy identification.

Suitability of Chains: The chains are suitable for the following cases.
(i) It is suitable for ordinary or preliminary works as its length alters due to continuous use.
(ii) Its length gets shortened due to bending of links and gets lengthened by flattening of the rings.
(iii) Being heavier, a chain gets sagged considerably when suspended at the ends.
(iv) It can be easily repaired in the field.
(v) Measurement readings can be taken very easily.
(vi) It is only suitable for rough works.
Merits of Chains:
(i) They can be read easily and quickly
(ii) They can withstand wear and tear
(iii)They can be easily repaired or rectified in the field.
Demerits of Chains:
(i) They are heavy and take too much time to open or fold.
(ii) They become longer or shorter due to continuous use.
(iii)When the measurement is taken in suspension the chain sags excessively giving incorrect measurements.

10
 KIIT POLYTECHNIC

ARROWS: Arrow are made of tempered steel wire of diameter 4mm.One end of the arrow is bent into a ring of
diameter 50 mm and the other end is pointed. Its overall length is 400mm. Arrows are used for counting the number
of chains while measuring a chain line. Generally 10 arrows accompany a chain.

RANGING RODS: Rods, which are used for ranging a line are known as ranging rod. Such rods are made of
seasoned timber or seasoned bamboo. Sometimes GI pipes of 25mm/ 30mm diameter are also used as ranging rods.
They are generally circular in section of diameter 25mm/30mm and length 2m / 3m.The rod is divided into equal
parts of 20cm each and the divisions are painted black and white or red and white alternatively so that the rod is
visible from a long distance. The lower end of the rod is pointed or provided with an iron shoe.

RANGING POLES: These are similar to ranging rods except that they are heavier in section of length 4m to 6m.
They are used for ranging very long lines in undulating ground.

OFFSET RODS: These are similar to ranging rods and o 3m long. The top is provided with an open hook for
pulling or pushing a chain through obstruction like bushes etc.It is used for aligning the offset line and measuring
short offsets.

PLUMB BOB: It is used to transfer the end points of the chain onto ground while measuring distances in hilly
terrain. It is also used for testing verticality of ranging poles, ranging rods.
PEGS: Wooden pegs usually 2.5cm square and 15cm deep are used to mark the position of survey stations.
ADJUSTMENT OF CHAIN: Chains are adjusted in the following ways-
(1) When the chain is too long, it is adjusted by
(a) Closing up the joints of the rings
(b) Hammering the elongated rings
(c) Replacing some old rings by new rings
(2) When the chain is too short, it is adjusted by
(a) Straightening the bent links
(b) Opening the joints of the rings
(c) Replacing the old rings by some larger rings
2.5 ERRORS IN LINEAR MEASUREMENTS / CHAINING
Errors in chaining may be caused due to variation in temperature and pull, defects in instruments etc. They may
be classified into two catagories.
11
 KIIT POLYTECHNIC

(i) Compensating errors

(ii) Cumulative error
(i) COMPENSATING ERRORS: Errors, which may occur in both directions (that is both positive and negative)
and which finally tend to compensate are known as compensating errors.
(ii) CUMULATIVE ERRORS: Errors, which may occur in the same direction and which finally tend to accumulate
are said to be cumulative. They seriously affect the accuracy of the work and are proportional to the length of
the line (L).The errors may be positive or negative.
I. Positive Cumulative Error: The error, which make the measured length more than the actual
is known as positive cumulative error.
Sources: (a) The length of chain / tape is shorter than its standard length due to
▪ Bending of links
▪ Removal of too many rings due to adjustment of its length.
▪ Knots in connecting links.
▪ The field temperature is lower than that at which the tape was calibrated.
▪ Shrinkage of tape when moist
▪ Clogging of rings with mud.
(b) The slope correction is ignored while measuring along slopping ground.
(c) The sag correction, if not applied when chain / tape is suspended at its ends.
(d) Incorrect alignment.
II. Negative Cumulative Error: The error, which make the measured length less than the actual is
known as negative cumulative error.
Sources: (a) The length of chain / tape is longer than its standard length due to
▪ Flattening of connecting rings.
▪ Opening of the ring joints.
▪ The field temperature is higher than that at which the tape was calibrated.
MISTAKES: Errors occurring due to the carelessness of the chainman are called mistakes. Following are a few
common mistakes:
(1) Once an arrow is withdrawn from the ground during chaining it may not be replaced in proper position, if
required due to some reason.
(2) A full chain length may be omitted or added. This happen when arrows are lost or wrongly counted.
(3)The number may be read from the wrong direction; for instance a 6 may be read as a 9.

12
 KIIT POLYTECHNIC

(4) Some number may be called wrongly. For example 50.2 may be called as fifty two without the decimal point
being mentioned.
PRECAUTIONS AGAINST ERRORS AND MISTAKES:
(1) The point where the arrow is fixed on the ground should be marked with a cross(×).
(2) The zero end of the chain or tape should be properly held.
(3) During chaining the number of arrows carried by the follower and leader should always tally with the total
number of arrows taken.
(4) The chainman should call the measurement loudly and distinctly and the surveyor should repeat them while
booking.
(5) Ranging should be done accurately.
(6) No measurement should be taken with the chain in suspension.
ERRORS IN MEASUREMENT DUE TO INCORRECT CHAIN / TAPE LENGTH:
Due to usage of chain over rough ground, its oval shaped rings get elongated and thus the length of chain gets
increased. On the other hand, sometimes some of the links get bent and consequently the length of the chain gets
decreased. Thus, the lengths obtained by chaining with a faulty chain are either too long or too short than the length
which would be obtained with a chain of standard length. If the chain is too long the measured distance will be less
and if the chain is too short the measured distance will be more.
Let L be the true length of chain and L’ be the faulty length of chain.
'
Then, the true length of a line = L  measured length
L
2.6 CORRECTIONS IN LINEAR MEASUREMENTS
(i) Correction for standard length
(ii) Correction for alignment
(iii) Correction for slope
(iv) Correction for tension
(v) Correction for temperature
(vi) Correction for sag

(i) Correction for standard length: Before using a tape, its actual length is ascertained by comparing it with a
standard tape of known length. The designated nominal length of a tape is its designated length e.g. 30m or
100m. The absolute length of a tape is its actual length under specified conditions.
Let L= measured length of a line

13
 KIIT POLYTECHNIC

Ca = correction for absolute length

l = nominal designated length of tape
C = correction be applied the tape
L.C
Then, Ca =
l
The sign of the correction Ca will be the same as that of C.

(ii) Correction for alignment: Generally a survey line is set out in a continuous straight line. Sometimes, it
becomes necessary, due to obstruction to follow a bent line which may be composed of two or more straight
portions subtending an angle other than 180º as shown in Fig.2.2.

A B

ϴ1 ϴ2

Fig.2.3. Correction for alignment

Let AC=l1; CB= l2

Angle BAC = ϴ1; Angle BAC = ϴ2
Length AB= l1 cos ϴ1 + l2 cos ϴ2
The required correction = (l1+ l2)-( l1 cos ϴ1 + l2 cos ϴ2)

(iii)Correction for slope: The distance measured along the slope between two stations is always greater than
the horizontal distance between them. The difference in slope distance and horizontal distance is known as
slope correction which is always substractive.

Fig. 2.4 Slope Correction

14
 KIIT POLYTECHNIC

Let L = slope distance AB

D = horizontal distance AC
h=difference in reduced levels of A and B

D= (L 2
− h2 )
h2
Slope Correction = L – D =
2L

(iv) Correction for pull/ tension (CP):

During measurement the applied pull may be either more or less than the pull at which the chain or tape
was standardized. Due to the elastic property of materials the strain will vary according to the variation of
applied pull and hence necessary correction should be applied. This correction is given by the expression
CP =((P-P0)xL)/(AxE)
where, P= Pull or tension applied during measurement in Newtons
A= Cross-sectional area of the tape in square cm.
L= Length of the measured line
P0 = Standard pull
E = Modulus of Elasticity of the tape
If the applied pull is more, tension correction is positive, and if it is less, the correction is negative.
(v) Temperature correction (Ct):
This correction is necessary because the length of the tape or chain may be increased or
decreased due to rise or fall of temperature during measurement. The correction is given by the expression
as mentioned below.
Ct = α(Tm-T0)L
where Ct = correction for temperature
α=coefficient of thermal expansion
Tm=temperature during measurement in degrees centigrade
T0=temperature at which the tape was standardized in degrees centigrade
L=length of tape
(vi) Correction for sag (Cs)
This correction is necessary when the measurement is taken with the tape in suspension. It is given
by the expression as mentioned below.

15
 KIIT POLYTECHNIC

2
L W 
Cs =  
24  P 
where W= total wt of the tape; L= horizontal distance between the supports
P = pull applied during measurement

Problem 1. The length of a survey line measured with a 30m chain was found to be 631.5m. When the chain was
compared with a standard chain, it was found to be 0.1m too long. Find the true length of the survey line.
Solution
L'
The true length of a line =  measured length
L
L’ = 30.1m. L = 30m
and measured length of the survey line = 631.5m
30.1
Thus, true length of the survey line =  631.5 = 633.603 m.
30

Problem 2. A 20m chain was found to be 4 cm too long after chaining 1400m. It was 8 cm too long at the end of
day’s work after chaining a total distance of 2420m. If the chain was correct before commencement of the work, find
the true distance.
Solution
The correct length of the at commencement = 20m
The length of the chain after chaining 1400m = 20.04 m.
The mean length of the chain while measuring = (20+20.04)/2 = 20.02m
The true distance for the wrong chainage of 1400m = (20.02/20)x1400 = 1401.4 m
The remaining distance = 2420-1400 = 1020m
The mean length of chain while measuring the remaining distance = (20.08+20.04)/2 = 20.06m
The true length of remaining 1020m = (20.06/20)x 1020 =1023.06m
Hence, the total true distance = 1401.4 + 1023. 06 = 2424.46 m Ans.

Problem No.3. A line was measured with a steel tape which was exactly 30 meters at 20℃ at a pull of 100N (or
10kgf), the measured length being 1650.00 meters. The temperature during measurement was 30° C and the pull
applied was 150N (or 15kgf). Find the length of the line, if the cross-sectional area of the tape was 0.025 sq.cm. The

16
 KIIT POLYTECHNIC

co-efficient of expansion of the material of the tape per 1 ºC =3.5x10−6 and the modulus of elasticity of the material
of the tape=2.1x105 N/m𝑚2 (2.1x106 kg/c𝑚2 ).
Solution:
(i) Correction of temperature per tape length

=𝛼(𝑇𝑚 − 𝑇𝑜)𝐿

= 0.0000035(30 − 20)𝑋 30

= 0.00105m (+ve)

(ii) Correction for pull per tape length

= CP =((P-P0)xL)/(AxE)=((150-100)x30)/(2.5x2.1x105)

=0.00286m (+ve)

Combined correction = 0.00105+0.00286=0.00391m

True length of the tape = 30+0.0039=30.0039m

True length of the line = (30.0039x1650.00)/30

=1650.21m.

Chapter-2

Chaining and chain surveying

In addition to chain or tape, several other auxiliary equipment are required in a chain surveying These are listed in
subsequent paragraphs.

Arrows
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. These are used to mark the end of each chain length as shown in Figure (a).

17
 KIIT POLYTECHNIC

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 (b).
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 with a hammer. These are kept at about 40 mm (minimum) projecting
above the ground.

Ranging Rods
These are octagonal or circular in plan normally 25 to 30 mm diameter straight timber or tubular steel rods, 3 m in
length and provided with an iron shoe at lower end as shown in Figure (c). These are painted in black and white
alternate bands and normally have a flag at the top for easy recognition and identification from a distance. If the ranging
roads are graduated in meters and one tenth of a meter, they are called offset rods and are used for measurement of
short offsets.
Plumb Bob
It is usually heavy spherical or conical ball, as shown in Figure (d), 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.

18
 KIIT POLYTECHNIC

Compass, Dumpy levels and. Theodolites are also positioned over the station point accurately with the help of plumb
bobs.
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 (e). 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.

Use of chain

Unfolding Of Chain: To open a chain the strap is unfastened and the two brass handles are held in the left hand and
the bunch is thrown forward with the right hand. Then on chainman stands at the starting station by holding one handle
and another moves forward by holding the other handle until the chain is completely extended.

Folding of Chain : After the completion of the work the chain should be folded in to a bundle and fastened with a
leather strap. To do this the handles of the chain should be brought together by pulling the chain at the middle.
Commencing from the middle, take two pairs of link at a time with the right hand and place them obliquely across the
other in the left hand. When the chain is collected in a bundle, it is tied with a leather strap. This process is called the
folding of chain.

Reading a chain :

A survey chain is generally composed of 100 or 150 links formed by pieces of galvanised mild steel wire of 4 mm
diameter. 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 centres of two
consecutive middle rings.
The ends of chain are provided with brass handles with swivel joints. 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 centre 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

Testing of a chain :
Due to continuous use, a chain may be elongated or shortened. So, the chain should be tested and adjusted accordingly.
If full adjustment is not possible, then the amount of shortening ( known as ‘too short’ ) and elongation ( known as
‘too long’ ) should be noted clearly for necessary correction applicable to the chain.

For testing the chain, a test gauge is established on a level platform with the help of standard steel tape. The steel tape
is standardised at 200C and under a tension of 8 kg. The test gauge consist of two pegs having nails at the top and fixed
on a level platform a required distance apart ( say 20 or 30m ). The incorrect chain is fully stretched by pulling it under
normal tension along the test gauge. If the length of the chain does not tally with standard length, then the attempt
should be made to rectify the error. Finally the amount of elongation or shortening should be noted.
19
 KIIT POLYTECHNIC

The allowable error is about 2mm per 1m length of the chain. The overall length of the chain should be within the
following permissible limit :

20 m chain : ± 5mm
30m chain : ± 8mm
Adjustment of a chain :

Chains are adjusted in the following ways :

➢ When the chain is too long, it is adjusted by :

• Closing the opened joints of the rings.
• Reshaping the elongated rings.
• Removing one or more circular rings.
• Replacing the worn-out rings.

➢ When the ring is too short, it is adjusted by:

• Straightening the bent links.
• Flattening the circular rings .
• Inserting the new rings where necessary.
• Replacing the old rings by some larger rings.

Ranging :

The process of establishing intermediate points on a straight line between two end points is known as ranging.
20
 KIIT POLYTECHNIC

Purpose of ranging :

The purpose of ranging is to mark a number of intermediate points on a survey line joining two stations in the field so
that the length between them may be measured correctly.

If the line is short or its end station is clearly visible, the chain may be laid in true alignment. But if the line is long or
its end station is not visible due to undulation ground, it is required to mark a number of points with ranging rods.

Code of Signals for Ranging

Sl.No. Signal by the Surveyor Action by the Assistant

1 Rapid sweep with right hand Move considerably to the right
2 Slow sweep with right hand Move slowly to the right
3 Right arm extended Continue to move to the right
4 Right arm up and moved to the right Plumb the rod to the right
5 Rapid sweep with left hand Move considerably to the left
6 Slow sweep with left hand Move slowly to the left
7 Left arm extended Continue to move to the left
8 Left arm up and moved to the left Plumb the rod to the left
9 Both hands above head and then brought down Correct
10 Both arms extended forward horizontally and the Fix the rod
hands depressed briskly
Direct ranging :

When intermediate ranging rods are fixed along the chain line, by direct observation from either end station, the process
is known as “Direct Ranging”. Direct ranging is possible when the end stations are inter visible. The following
procedure is adopted for direct ranging :

• Erect ranging rods or poles vertically behind each end of the line.
• Stand about 2m behind the ranging rod at the beginning of the line.
• Direct the assistant to hold a ranging rod vertically at arm’s length at the point where the intermediate station
is to be established.
• Direct the assistant to move the rod to the right or left , until the ranging rods appear to be exactly in a straight
line.
• Stoop down and check the position of the rod by sighting over their lower ends in order to avoid error to non-
vertically of the ranging rods.
• After ascertaining that the ranging rods are in a straight line, signal the assistant to fix the ranging rod.

Indirect ranging :

When the end stations are not inter visible due to there being high ground between them, intermediate ranging rods are
fixed on the line in an indirect way. This method is known, as indirect ranging or reciprocal ranging. The following
procedure is adopted for indirect ranging.

Suppose A and B are two end stations which are not intervisible due to high ground existing between them.
Suppose it is required to fix intermediate points between A and B. Two chain men take up positions at R1 and S1 with
21
 KIIT POLYTECHNIC

ranging rods in their hands. The chainman at R1 stands with his face towards B so that he can see the ranging rods at
S1 and B. Again the chainman at S1 stands with his face towards A so that he can see the ranging rods at R1 and A.
Then the chainmen proceed to range the line by directing each other alternately. The chainman at R 1 direct the
chainman at S1 to come to position S2 so that R1 , S2 and B are in the same straight line. Again the chainman at S2
directs the chainman at R1 to move the position at R2 so that S2 , R2 and A are in the same straight line. By directing
each other alternately in this manner, they change their positions every time until they finally come to the positions R
and S,which are in the straight line AB. This means the points A, R, S and B are in the same straight line.

Role of Leader and Follower :

The chainman at forward end of the chain, who drag the chain forward, is known as
leader. The duties of the leader are as follows:
a. To drag the chain forward with some arrows and a ranging rod.
b. To fix arrows on the ground at the end of every chain.
c. To obey the instructions of the follower.

The chainman at the rear end of the chain, who holds the zero end of the chain at the
station, is known as the follower. The duties of the follower are :
a. To direct the leader at the time of ranging.
b. To carry the rear handle of the chain.
c. To pick up the arrows inserted by the leader.
Chaining on Level Ground :

Before starting the chaining operation two ranging rods should be fixed on the chain line, at the end stations.
The other ranging rods, should be fixed near the end of each chain length, during the ranging operation.

To chain the line, the leader moves forward by dragging the chain and by taking with him a ranging rod and
10 arrows . The follower stands at the starting station by holding the other end of chain. When the chain is fully
extended , the leader holds the ranging rod vertically at arm’s length. The follower directs the leader to move his rod
to the left or right until the ranging rod is exactly in line. Then the follower holds the zero end of the chain by touching
22
 KIIT POLYTECHNIC

the station peg. The leader stretches the chain by moving it up and down with both hands, and finally places it on the
line. He then inserts an arrow on the ground at the end of the chain and marks with a cross ( X ).

Again, the leader moves forward by dragging the chain with nine arrows and the ranging rod. At the end of the
chain, he fixes another arrow as before. As the leader moves further, the follower picks up the arrows which were
inserted by the leader. During chaining the surveyor or an assistant should conduct the ranging operation.

In this way, chaining is continued. When all the arrows have been inserted and the leader has none left with
him, the follower hands them over to the leader; this should be noted by the surveyor. To measure the remaining
fractional length, the leader should drag the chain beyond the station and the follower should hold the zero end of the
chain at the last arrow. Then the odd links should be counted.

Chaining on Sloping Ground:

Chaining on the surface of a sloping ground gives the sloping distance. For plotting the surveys, horizontal
distances are required. It is therefore, necessary either to reduce the sloping distance to horizontal equivalent or to
measure the horizontal distances between the stations directly. The following are the different methods that are
generally employed.

a) Direct Method or Stepping Method

b) Indirect Method

Direct Method:

This method is applied when slope of the ground is very steep. In this method, the sloping ground is divided in
to a number of horizontal and vertical strips, like steps. So, this method is also known as stepping method. The length
of the horizontal portions are measured and added to get the total horizontal distance between the points. The steps
may not be uniform, and would depend on the nature of the ground.

Procedure:

Suppose the horizontal distance between points A and B is to be measured.

The line AB is first ranged properly.
Then, the follower holds the zero end of the tape at A.
The leader selects a suitable length AP1 so that P1 is at chest height and AP1 is just horizontal.
The horizontal is maintained by eye estimation, by tri-square or by wooden set-square.

23
 KIIT POLYTECHNIC

The point P2 is marked on the ground by plumb-bob so that P1 is just over P2.
The horizontal length AP1 is noted then the follower moves to the position P2 and holds the zero end of the tape at that
point.
Again the leader selects a suitable length P2P3 in such a way that P2P3 is horizontal and P3P4 vertical.
Then the horizontal lengths P2P3 and P4P5 are measured.
So the total horizontal length, AB = AP1 + P2P3 + P4P5
Indirect Method :

When the slope of the ground surface is long and gentle, the stepping method is not suitable. In such a case,
the horizontal distance may be obtained by the indirect methods. Those are of following types.

a. By measuring the slope with clinometers.

b. By applying hypotenusal allowance
c. By knowing the difference of level between the points.
a. Measuring slope with a clinometer :

A clinometers is a graduated semicircular protractor. It consists of two pins P1 and P2 for sighting the object. A plum
bob is suspended from point O with a thread. When the straight edge is just horizontal, the thread passes through 00.
When the straight edge is tilted, the thread remains vertical, but passes through a graduation on the arc which shows
the angle of slope.

Suppose C and D are two points on sloping ground. Two ranging rods are fixed at these points. Then two other points
C1 and D1 are marked on the ranging rods so that CC1 = DD1

The clinometers is placed in such a way that its centre just touches the mark C1. The clinometers is then
inclined gradually until the points P1, P2, and D1 are in the same straight line. At this position the thread of the
clinometers will show an angle which is the angle of slope of the ground. Suppose this angle is α . The sloping distance
CD is also measured.

The required horizontal distance = CB = lcosα

24
 KIIT POLYTECHNIC

b. Applying hypotenusal allowance

In this method , the slope of the ground is first out by using the clinometers. Hypotenusal allowance is then
made for each tape length.
Let 𝜃= angle of slope measured by clinometers
AB = AB1 = 20m = 100 links
AC = AB sec𝜃 = 100 sec 𝜃
B1C = AC – AB1
= 100 sec 𝜃 - 100
= 100 (sec𝜃 − 1)

Obstacle:

A chain line may be interrupted the following situations:

1. When chaining is free, but vision is obstructed.

2. When chaining is obstructed, but vision is free, and
3. When chaining and vision are both obstructed

1. Chaining free but vision obstructed:

Such a problem arises when a rising ground or a jungle area interrupts the chain line. Here the end stations
are not inter-visible.

Case – I

The end stations may be visible from some intermediate points on the rising ground. In this case, reciprocal
ranging is resorted to, and the chaining is done by stepping method.

Case – II

The end stations are not visible from intermediate points when jungle are comes across the chain line.

25
 KIIT POLYTECHNIC

Let AB line be the actual chain line which can not be ranged and extended because of interruption by a jungle. Let line
extended up to R. A point P is selected on the chain line and a random line PT is taken in a suitable direction. Points
C, D and E are selected on the random line and perpendiculars are projected from them. The perpendicular at C meets
the line at 𝒄𝟏

Theoretically,
𝐷𝐷1 𝐶𝐶1
=
𝑃𝐷 𝑃𝐶

𝐷𝐷1 = 𝐶𝐶1 x PD .......................................................... (1)

𝑃𝐶

Again from triangle 𝑃𝐸𝐸1and 𝑃𝐶𝐶1

𝐸𝐸1 𝐶𝐶1
=
𝑃𝐸 𝑃𝐶

𝐸𝐸1 = 𝐶𝐶1 x PE .......................................................... (2)

𝑃𝐶

From eq 1 and 2, the lengths 𝑫𝑫𝟏 and 𝑬𝑬𝟏 are calculated. The distance is measured along the perpendiculars at D and
E. Points 𝑫𝟏 and 𝑬𝟏 should lie in the chain line AB

Distance 𝑷𝑬𝟏 = √𝑷𝑬𝟐 + 𝑬𝑬𝟐𝟏

2. Chaining obstructed but vision free:

Such a problem arises when a pond or river comes across the chain line. The stations may be tackled in the
following ways.

Case – I

When a pond interrupts the chain line, it is possible to go around the obstruction.

26
 KIIT POLYTECHNIC

CD = EF

CD = √𝐸𝐷2 + 𝐶𝐸2
3. Chaining and vision both obstructed :

Such a problem arises when a building comes across the chain line. It is solved in the following manner.

Suppose AB is the chain line. Two points C and D are selected on it at one side of the building. Equal
perpendiculars CC1 and DD1 are erected. The line C1D1 is extended until the building is crossed. On the extended
line, two points E1 and F1 are selected. Then perpendiculars E1E and F1F are so erected that

E1E = F1F = D1D = C1C

Thus, the points C, D, E and F will lie on the same straight line AB

Here, DE = D1E1

The distance D1E1 is measured , and is equal to the required distance DE.

Problem :

A chain line ABC crosses a river, B and C being on the near and distant banks respectively. The line BM of
length 75 m is set out at right angles to the chain line at B. If the bearings of BM and MC are 287 0 15’ and
620 15’ respectively, find the width of the river.

Solution :

<BMC =BB of BM – FB of MC
i.e. 𝛼 = (287015′ − 18000′) − 62015′ = 4500′
From triangle MBC, 𝐵𝐶 = 𝑡𝑎𝑛4500′
𝐵𝑀
𝐵𝐶 = 𝐵𝑀 𝑡𝑎𝑛4500′ = 75 𝑚
27
 KIIT POLYTECHNIC

So the width of river is 75 m.

CHAIN SURVEYING

Definition:

The chain surveying is one of the method of land surveying. It is the system of surface in which sides
of different triangular are measured directly in the field and no angular measurement are taken.

Principle of Chain Surveying:

The principle of chain surveying is triangulation. This means that the area to be surveyed is divided in to a
number of small triangles which should be well conditioned. In chain surveying the sides are directly measured by
chain or tape.

Chain surveying is recommended when:

1. The ground surface is more or less leveled.

2. A small area is to be surveyed.
3. A small – scale map is to be prepared and
4. The formation of well conditioned triangles is easy

Chain surveying is unsuitable when:

1. The area is crowded with many details.

2. The area consists of too many details.
3. The area is very large.
4. The formation of well – conditioned triangles becomes difficult due to obstacles.

Well Conditioned Triangle:

1. A triangle is said to be well – conditioned when no angle is less than 300 or greater than 1200. An ideal triangle
is considered to be best conditioned or ideal triangle.
2. Well conditioned triangles are preferred because their apex points are very sharp and can be located by single
‘dot’.

Well-Conditioned Triangle

Ideal Triangle

28
 KIIT POLYTECHNIC

ILL – Conditioned Triangle:

1. A triangle in which an angle is less than 300 and greater than 1200 is said to be ill-conditioned triangle.
2. Ill conditioned triangles are not used in chain surveying.

0
20

0
25

Ill-Conditioned Triangle

Accessories in chain survey

The following equipments are required for conducting chain survey:

1. Metric chain (20 m) = 1 no

2. Arrows = 10 nos
3. Metallic tape (15m) = 1 no
4. Ranging rods = 3 nos
5. Offset rod = 1 no
6. Clinometer = 1 no
7. Plumb bob with thread = 1 no
8. Cross staff or optical square = 1 no
9. Prismatic compass with stand = 1 no
10. Wooden pegs = 10 nos
11. Mallet = 1 no
12. Field book = 1 no
13. Good pencil = 1 no
14. Pen knife = 1 no
15. Eraser = 1 no

Reconnaissance Survey and Index Sketch:

29
 KIIT POLYTECHNIC

During reconnaissance survey, the surveyor should walk over the area and note the various obstacles and
whether or not the selected stations are inter-visible. The main station should be so selected that they enclose the whole
area. The surveyor should be take care that the triangles formed are well-conditioned.

The neat hand sketch of the area which is prepared during reconnaissance survey is known as “index sketch”
or “key plan”. The index sketch shows the skeleton of survey work.

Selection of Surveying Stations:

Survey stations are the points at the beginning and the ending of a chain line. The stations are classified under
3 categories

i.e - (a) Main Station

(b) Subsidiary Station
(c) Tie Station
1. Main survey station at the end of chain line should be inter-visible.
2. Survey line should be minimum as possible.
3. The main principle of surveying such as working from whole to part and from part to whole.
4. The stations should be well conditioned triangle.
5. Every triangle should be provided with a check line.
6. Tie line should be provided to avoid too long offsets.
7. Obstacles to ranging and changing if any should be avoided.

The larger side of the triangle should be placed parallel to the boundaries, roads, buildings, etc. to have short offsets.

1. Chain line should be lie over leveled ground.

2. Line should be laid on one side of the road to avoid disturbance of chaining by passing of traffic.

INDEX SKETCH

Base line:

30
 KIIT POLYTECHNIC

The line on which the frame work of the survey is built is known as the “Base line”. It is the most
important line of the survey work. Generally, the longest of the main survey line is considered as base line.

Tie line:

The tie line is a line which joins subsidiary stations on the main line.

Check line:

The line joining the apex point of triangle to some fixed point on its base is known as check line. It is
taken to check the accuracy of the triangle.

Offset:

The lateral measurement taken from an object to the chain line is

known as offset. Offsets are taken to locate objects with reference to the
chain line. They are two types:

I. Perpendicular Offset
II. Oblique Offset

Perpendicular Offset:

When the lateral measurement for fixing the detail points are maid perpendicular to the chain line. The
offsets are known as perpendicular offset.

Oblique Offset:

When the lateral measurement for fixing the detail points are maid at any angle to the chain line. The
offsets are known as oblique offset. It can be done by following two(2) process
i.e -
a. Long offset
b. Short offset
Setting offset with chain and tape (Manual methods)

3-4-5 Offset

Perpendicular offset of chain line at any point A is obtained using the following mathematical expression (32
+ 42 = 52). A point B is located on chain line at a distance of

31
 KIIT POLYTECHNIC

3 m from A such that AB = 3 m. Next, an arc is set on ground with centre at A and radius equal to 4 m. Another
arc is laid with center at B and radius equal to 5 m intersecting the previous arc at C as shown in Figure (a).
Line AC will then be perpendicular to line AB.

Swing Offset
The perpendicular distance of an important feature, e.g. building corner, from the chain line is measured using
swing offset method. The zero end of tape is kept at point of interest (Figure (b)) and point A (i.e. normal from
C on chain line) is located by swinging the tape with C as center. The point A is characterized by a point at which
the arc generated by swing is tangential to survey line and the distance of C from any point on chain line is
minimum.

It may be noted that usually only small offsets can be set by manual methods.

Optical Square:

1. It is a most suitable instrument for setting out a line at a right angle to another line.
2. It consists of a circular metal box about 5c.m. in diameter and 1.25c.m. in deep. It consists of two inclined
mirror at an angle of 450.
3. The upper glass is known as horizontal glass and the lower end glass is known as index glass.

Principle:

32
 KIIT POLYTECHNIC

If the two mirror’s are inclined with the surface at an angle of 450. The plane is successfully reflected under
deviation of twice the angle.

Uses:

1. It is used to find out foot of perpendicular to the chain line.

2. To set out a perpendicular to a chain line.

Cross staff:

The cross-staff consists of four metal arms with vertical slits. The two pairs of
arms are at right angles to each other. The vertical slits are meant for sighting the
ranging rods. The cross-staff is mounted on a wooden pole of length 1.5m. and diameter
2.5c.m. The pole is fitted with an iron shoe.

Limiting Length of Offset:

The maximum length of the offset should not be more than the length of the tape used in the survey. Generally , the
maximum length of offset is limited to 15 m. however, this length also depends upon the following factors:

(a) The desired accuracy of the map

(b) The scale of the map
(c) The maximum allowance deflection of the offset from its true direction
(d) The nature of ground

Sources of Errors :

Errors may arise from three sources :

(1) Instrumental
Error may arise due to imperfection or faulty adjustment of the instrument with which measurement is being
taken. For example, a tape may be too long or an angle measuring instrument may be out of adjustment. Such
errors are known as instrumental arrors.
(2) Personal
Error may also arise due to want of perfection of human sight in observing and of touch in manipulating
instruments. For example, an error may be there in taking the level reading or reading an angle on the circle of
a theodolite. Such errors are known as personal errors.
(3) Natural
Error may also be due to variations in natural phenomena such as temperature, humidity, gravity, wind,
refraction, and magnetic declination. If they are not properly observed while taking measurements, the results

33
 KIIT POLYTECHNIC

will be incorrect. For example a tape may be 20 metres at 200C but its length will change if the field temperature
is different.

Field Book:

1. The book in which the chain or tape measurements are entered or sketched of detail points are recorded is called
field book.
2. Its size is 20c.m.X 12c.m.
3. The chain line may be represented about 1.5c.m. to 2.0c.m. a part rolled down the middle of each page.
4. The chain line is started from the bottom of page and work up words.
5. It should be well bounded and a size of convenient for the pocket.
6. All distance along the chain line are entered either to the left or to the right of the chain line.
7. The new line should be started from a new fresh page and name of line should be noted at the foot and booking
proceeds from the bottom of the page to up wards.
8. At the different feature within the offset are reached, surveyor draw them and enters the chain and length of
each offset.
9. Field books may be two types
I. Single Line
II. Double Line

Single-Line Field Book

In this type of field book , a single red line is drawn through the middle of each page. This line represents the chain
line and the chainages are written on it. The offsets are recorded with sketches to the left or right of the chain line.

Double-Line Field Book

In this type of field book, two red lines, 1.5 cm apart, are drawn through the middle of each page. This column
represents the chain line, and the chainages are written in it. The offsets are recorded with sketches to the left or right
of this column.

34
 KIIT POLYTECHNIC

EQUIPMENTS OF PLOTTING:

Following are the equipments of plotting

1. Drawing board ( normal size – 1000 mm X 700 mm)

2. Tee – Square
3. Set – square (450𝑎𝑛𝑑600)
4. Protractor
5. Cardboard Scale
6. Instrument box
7. Drawing sheets

Procedure for plotting:

1. A suitable scale is chosen so that the area can be accommodated in the space available in the map.
2. A margin of about 2 cm. from the edge of the sheet is drawn around the sheet.
3. The north line marked on the right-hand corner, and should perfectly be vertical. When it is not convenient to
have a vertical north line, it may be inclined to accommodate the whole area within the map.

35
 KIIT POLYTECHNIC

4. The framework is completed with all survey lines, check lines and tie lines. If there is some plotting errors
which exceeds the permissible limits, the incorrect lines should be resurveyed.
5. The plotting of offsets should be continued according to the sequence maintained in the field book.
6. The conventional symbols are used in the map should be shown on the right – hand side.
7. The scale of the map is drawn below the heading or in some suitable space. The heading should be written on
the top of the map.
8. Unnecessary lines, objects, etc. should be erased.
9. The map should not contain any dimensions.

Recommended scales for some of the types of map could be

(a) Geographical Maps : 1/25000 to 1/100000 and even smaller. Atlas maps and wall maps
could even have smaller scales.
(b) Topographical Maps : 1/25000 to 1/250000 showing natural and man-made features and
contours.
(c) Cadastral or Land Revenue Maps : 1/500 to 1/5000, relatively larger scales showing
holdings of individuals. Used for tax/revenue collection and for planning and management.
(d) Building Sites, Town Planning Schemes etc. : 1/5000 to 1/10000, for building sites
larger scale, e.g. 1/1000 can be used.
(e) Roads, Railway Lines or Canal Maps : Longitudinal sections can be drawn to a horizontal scale of
1/1000 to 1/20000 while for vertical plots the scales are 1/100 to 1/200. For plotting cross sections, both
horizontal and vertical scales are 1/100 to 1/200.

It can be noted that on many maps with smaller scales, many important land features cannot be plotted to scale.
However, these, being important details, cannot be ignored. Hence, these are represented on map sheet by
suitable conventional symbols.

Some of the conventional symbols approved by Bureau of Indian Standard (BIS) are as shown in Figure.

36
 KIIT POLYTECHNIC

ERRORS IN CHAIN SURVEYING:

Errors in chaining may be caused due to variation in temperature and pull, defects in instruments,
etc. They may be either;

1. Compensating Error
2. Cumulative Error

Compensating Error:

Errors which may occur in the both directions (i.e. both positive and negative) and which finally tend to
compensate are known as compensating errors. They are proportional to √𝐿 , where √𝐿 - is the length of the line. Such
error may be caused by

1. Incorrect holding f the chain.

2. Inaccurate measurement of right angles with chain, tape.
3. Horizontality and verticality of steps not being properly maintained during the stepping operations.
4. Fractional parts of the chain or tape not being uniform throughout its length

Cumulative Error:

Errors which may occur in the same direction and which finally tend to accumulative. They seriously affect
the accuracy of work, the length of the line (L).

Positive Error: when the measured length is greater than the actual length,(the chain length is too short), the error is
said to be positive error. Such error occur due to:

(a) The length of chain or tape being shorter than the standard length.
(b) Slope correction not being applied.
37
 KIIT POLYTECHNIC

(c) Correction for sag not being made.

(d) Measurement being taken with faulty alignment.
(e) Measurement being taken in high winds with the tape in suspension.

Negative Error: When the measured length is less than the actual length,(the chain length is too long), the error is said
to be negative . These errors occur when length of chain or tape is greater than the standard length due the following
reasons :

(a) The opening of ring joints.

(b) The applied pull being much greater than the standard.
(c) The temperature during measurement being much higher than standard.
(d) Wearing of connecting rings.
(a) Elongation of the links due to heavy pull.

Precautions against Error:

Following are the precautions should be taken to guard against errors and mistakes.
1. The point where the arrow is fixed on the ground should be marked with a cross (X).
2. The zero end of the chain or tape should be properly held.
3. The chain man should call the measurement loudly and distinctly and the surveyor should repeat them while
booking.
4. During chaining , the number of arrows carried by the follower and leader should always tally with the total
numbers of arrows taken.
5. Measurements should not be taken with tape in suspension in high wind.
6. In stepping operations, horizontality and verticality should be properly maintained.
7. Ranging should be done accurately.
8. No measurement should be taken with the chain in suspension.
9. Care should be taken so that the chain is properly extended.
Chapter-3
Angular measurement and compass surveying
Compass:

The compass works on the principle that a freely suspended magnetic needle takes the direction of the
magnetic lines of force at a place. This provides us a reference direction with respect to which all angles can
be measured.

There are two types of compasses

1. The prismatic compass

2. The surveyor’s compass.
The surveyor’s compass is rarely used in comparison purposes. The principle of the operation of both
the compass is the same but they are made differently used in the field

1) The prismatic compass.

38