Chain Surveying
Content
The Metric Chain and Tape
Accessories for Chain Survey
Ranging a Line
Measuring along Slope
Corrections to Measurements
Chain Survey
Problems in Chaining
Obstacles to Chaining
METRIC CHAIN AND TAPE
Metric chains come in lengths of
5 m, 10 m, 20 m and 30m
Older chains were in 100
feet(engineers),66 feet
(Gunter’s) and 33 feet (revenue)
Chains have tallies and rings to
identify intermediate values
METRIC CHAINS
Made of 4mm galvanized iron
wire
Made of links 200 mm long
and connected by circular or
oval rings
End links shorter for providing
handles
5M AND 10M CHAINS
HANDLES,RINGS AND TALLIES
METRIC TAPE
TAPES
Cloth tape
Metallic tape
Steel tape
Invar tape
Cloth or linen tapes are not good for
field work as they shrink, tear easily
and hence not suitable for survey
work.
Metallic tapes
Lengths of 2m, 5m, 10 m, 20m, 30m,
50m etc.
Yarn interwoven with metal fibers
Metal ring to hold at the outer end
16 mm wide, marked in cm and m
Rolled out by pulling and rolled back
using rotating handle
Commonly used for ordinary survey
work
STEEL TAPE
Steel tapes are made of galvanized steel or
stainless steel
Lengths from 1 m to 50 m
Marked
in
meters,
decimeters
and
centimeters with end section in millimeters
Costly but very accurate
Can be pulled out with the handle and
rolled back automatically
Used for accurate survey work
INVAR TAPE
Made of an alloy of steel and nickel
About 6 mm wide and in lengths of
30m, 50 m and 100m
Very low thermal coefficient
Used for very precise work as in
base line measurement
Should be handled very carefully
ACCESSORIES FOR CHAIN SURVEYING
1.Ranging rods
2.Ranging poles
3.Arrows
4.Offset rod
5.Wooden pegs
6.Laths and whites
7.Other equipment for
bushes, cleaning ground
clearing
ACCESSORIES
RANGING
Ranging required when line is
longer than a chain/tape length
Placing a line along the shortest
distance between points
When end stations are inter-visible,
direct ranging can be done
When end stations not inter-visible,
indirect ranging is done
Direct Ranging
Procedure for Direct Ranging
 Let us assume that A and B are end points of a survey line
visible from one another. Two ranging rods are fixed vertically
at stations A and B of survey line.
 The surveyor standing behind the ranging rod at A and looks
towards B and directs the assistant to move in the chain line
and establishes an intermediate station “C”. The point “C”
should lie in the straight line
 joining AB. The surveyor then directs the assistant to move his
ranging rod to right or left until the three ranging rods at A, C
and B appear to be exactly in a straight line.
 Similarly, any number of intermediate stations can be
established between two end stations. Measure the distance
between A and B and record it in observation sheet.
Indirect Ranging
Procedure for indirect ranging
Let A and B be two stations across a hill. A
ranging rod placed at one of them is not visible
from the other. The following may be followed
for ranging.
1. As shown in fig. above, select two
intermediate points C and D such that ranging
rods at B and D are visible from C and ranging
rods at A and C are visible from D. Also A, C, D,
B should be nearly as possible in a straight line.
2. The person at C looks towards B and directs
the man at D to fix his ranging rod in a manner
such that C, D, B are in one straight line.
3. Now the person at D looks towards the
ranging rod at A and directs the man at C to
fix his ranging rod at a place such that A, C
and
D
are
in
one
straight
line.
4. Steps 2 and 3 above are repeated till the
person at C finds C, D,. B to form a straight
line and simultaneously, the person at D finds
A, C, D also to form a straight line, then all the
four points A, C, D, and B are lie in straight
line.
Measuring distance along a slope
For plotting, horizontal distances are required
For a measured distance along slope,
horizontal distance can be calculated.
Horizontal length is less than length along
slope
For a given horizontal distance, slope
distance can be calculated
The increase in length along slope is called
hypotenuse allowance
Methods of measuring distance along the slope
Step Chaining
Slope distance and slope angle
Hypotenuse allowance
Step Chaining
The distance is measured in small
bits of horizontal distances, this is
known as step chaining.
Distance AB=AC’+CD’+DE’+EF’+FB’
Slope distance and slope angle
Slope angle measured
When slope angle is
known
Hypotenuse allowance
 Is the additional distance
measured along the slope to
give a chain length horizontally
Hypotenusal
allowance is given
by; L [sec θ – 1],
Corrections on Measured distances
1.Wrong length
2. Sea level
3. Slope
4.Temperature
5.Pull
6.Sag
Incorrect Length
Incorrect length Cont.
Chain or Tape long or short
Correction = (L’/L) x measured length
Where L is designated length
L’ is actual length of chain/tape
Correction to area = (L’/L)²x
measured area
Correction to volume = (L’L)³x
measured volume
Slope
Cs = h²/2L .
Where;
h – difference in height between the
end points of the line
L- Distance measured
Mean Sea Level Correction
 All distances should be reduced to their
equivalent mean sea level
 For θ<<<<small;
 M=Rθ ………………(i)
 L=θ(R+H)…………...(ii)
 Cmsl=M-L
=Rθ -θ(R+H)
=-θH
From (ii) θ=L/R+H
Hence Cmsl =-HL/R+H
Since R>>>H; R+H≈R
 Cmsl =-HL/R
 H - Height above sea level of place of
measurement
 L - measured distance
 R – Radius of the earth
Temperature Correction
CT = ± Lα(T – T’),
Where L = Length
α = Coefficient of thermal
expansion
(12 x 10^(-6) for steel tape)
T is the field temperature and
T’ is the standardizing temperature
Force Correction
Correction for pull = ± (P – P’)L/AE
Where P is the pull applied during
measurement
P’ is the pull while standardizing the tape
L is the length
A is the area of cross section of tape
E is the Young’s modulus of elasticity
(200 GN/m²)
Sag Correction
Csag = Lw²/24n²P²
L is the length
w is the weight per meter
n is the number of spans
P is the pull applied