Surveying I: 3 Chain Surveying: IOE class notes 2011, compiled by: Vishwa Nath Khanal

3.0 CHAIN SURVEYING (2 hours)

[Introduction; Principle and methods of chain survey, Terms used in chain survey; Field instruction
of chain survey]

3.1 Introduction
Chain surveying is that method of surveying in which the length of the lines are measured in
the field with chains, and no angular measurements are taken. It is suitable and well adapted
to the survey of small areas when the ground is fairly level and open with small details. It is
unsuitable when the ground is with many details. Chain, tape, ranging rods, and arrows are
the equipment used in chain surveying. Chain surveying is the simplest and accurate
method. A good knowledge of chain surveying is essential to a proper knowledge of
surveying as a whole.

3.2 Principle and methods of chain survey

D N C

ROAD

Temple
Park
E

Play ground
M

A O B
Main survey stations: A, B, C, and D Tie line: MN and OP
Main survey lines: AB, AC, AD, BC and CD Check line: BF and DE
Base line: AC Subsidiary stations: M, N, O and P

Figure: Chain survey [Survey stations and Survey lines]

The first principle of any type of surveying is to work from whole to the part. The
principle of chain surveying is triangulation. This means that the area is divided into a
series of standard geometric figure consisting of a number of connected triangles. The
sides of the triangles are measured directly in the field by chain or tape. Plotting

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 Surveying I: 3 Chain Surveying: IOE class notes 2011, compiled by: Vishwa Nath Khanal

triangles require no angular measurements, as a triangle is the simple figure that can be
plotted precisely from the measured length of its sides.
To get good result in plotting, the best form is equilateral triangle. Due to the
configuration of ground, it is not always possible to have equilateral triangles. Therefore
attempts should be made to have well conditioned triangles. Well conditioned triangle
means as nearly equilateral as possible and no angles should be less than 30°. The size
of the triangles will depend on the configuration of the country, but they should be as
large as possible.

3.3 Terms used in chain survey

Base line: The base line or backbone line is the longest of the main survey line which runs
through the middle of the area to be surveyed. The base line is the most important line, as it
is used for building up the frame work of triangles. While plotting, the base line is drawn first
on the sheet. Various survey stations are plotted with reference to the base line.f
Tie line: The chain line joining the two subsidiary stations is known as tie line. The main
object of running a tie line is to take the details of objects which are far away from the main
survey lines. A tie line also serves the purpose of a check line.
Check line: The lines which are run in the field to check the accuracy of the field work is
called the check line. The length of the check line measured in the field must agree with its
length on the plan. A check line may be laid by joining the apex of the triangle to any point
on the opposite side or by joining two points on any two sides of a triangle. Each triangle
must have a check line.
Survey station: The intersection points of the survey lines are called stations. Survey stations
are established after a reconnaissance survey of the field. Survey stations should be marked
so that they can be found again at any time during the survey work. Wooden pegs may be
driven in soft ground leaving a small projection above the ground. The name of the stations
is also written on the peg. Nails may be used in road but they should be flushed with
pavements. If a survey is small enough to be completed in a few hours, stations may be
marked by cutting out small sods or any such temporary devices.

Main survey station: Stations along the boundary of an area are known as main survey
stations. Main survey stations are prominent points at the beginning and at the end of
survey lines, which are connected by main survey lines to form the triangles. Main stations
are indicated by a small triangle.
Subsidiary station: Station on the main survey lines that divides area into triangle for
locating interior details are known as ‘subsidiary stations’. Subsidiary stations are indicated
by a circle.
Details: Details are the natural and man-made features on the surface of the earth. The
relative position of details (trees, stream bends, drains, boundaries, roads, buildings, lamp
posts etc) can be located by measurement of a distance and angle (usually 90°) from a point

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 Surveying I: 3 Chain Surveying: IOE class notes 2011, compiled by: Vishwa Nath Khanal

on a chain line. Position of a detail point can be located by measuring the distance of the
point from two separate points on the chain line.
Offset: An offset is the lateral distance of an object or ground features from the survey line.
Offsets are taken from the survey line to determine the location of details. The offsets are
generally measured with metallic tape in chain surveying. For every offset, the length of
offset and the distance along the chain line should be measured.
Degree of precision in measuring the offset mainly depends on the scale of plotting.
Normally, the limit of precision in plotting is 0.25mm. If the scale of plotting is 1:200 or 1cm
= 2m, 0.25mm on paper will correspond to 2 x 0.25mm = 50mm = 5cm on the ground. Hence
in such a case, the offset should be measured to the nearest 5cm.
Offsets are of two types: Perpendicular offset, and oblique offset.
Perpendicular offset: When the angle of offset is 90°, it is called perpendicular offset. It is a
lateral measurement taken at right angles to the chain line from the point of object.
Oblique offset: When the angle of offset is other than 90°, it is called an oblique offset.
Oblique offsets are taken to locate the details at a greater distance from the chain line for
important details such as corner of building or boundary pillar of adjoining properties. These
are also sometimes used for checking the accuracy of perpendicular offsets. As shown on
figure, two oblique offsets are taken from M and N on chain line AB to locate the position of
the corner of building drawing two arcs.

P P
Building

Length of
Chainage Perpendicular offset

M N B
M B A
A
Perpendicular offset Oblique offset

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 Surveying I: 3 Chain Surveying: IOE class notes 2011, compiled by: Vishwa Nath Khanal

If the object has a straight boundary,

one offset at each end is sufficient.

Straight boundary

If the object changes its direction, one offset should

be taken at each change of direction.

Straight object changing its direction

If the feature is irregular, offsets must be taken at

each change wherever there is a change in direction.

Post Post

Gate If the object is gate, locate both posts accurately

by taking offsets. Also, measure the width of gate.

3.4 Field Instruction or Field Procedure of Chain Survey

Equipment: Equipment required in chain survey are:
1. A chain 2. Arrows – 10 nos 3. Ranging rods
4. A tape 5. Field Book 6. Plumb bob
7. Pegs, Hammer 8. An instrument for setting out right angles
Steps in chain survey are:
 Reconnaissance
 Marking or fixing survey stations
 Reference sketch or General sketch of the field
 Location sketch of survey stations
 Running survey lines, taking details, providing check line and tie line etc.
Reconnaissance: Before starting the actual detail survey, surveyor should have a thorough
knowledge of the field to be surveyed. The preliminary inspection of the area to be surveyed
is called reconnaissance. The surveyor should walk around the area to have an idea of
terrain and the principal features of the ground so that he can decide the best layout of the
chain lines and the best location of survey stations. During reconnaissance, a reference
sketch of the ground should be prepared showing principal features such as buildings, roads,
streams, boundaries etc. Before selecting the control stations, the surveyor should examine
the inter-visibility of stations. The surveyor also forms an idea of the difficulties that may
arise, the time required, and the plan of work.

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 Surveying I: 3 Chain Surveying: IOE class notes 2011, compiled by: Vishwa Nath Khanal

Location sketch: Location sketch of survey stations is required to re-establish the positions
of the survey stations at a future date. After the station has been marked, its distance with
reference to two or three permanent object should be measured. These measurements are
recorded by drawing a reference sketch (location sketch) in the field book. Although two
measurements are sufficient to locate a station from the two reference point, a third
measurement is taken to serve as a check. The permanent point should be definite and
easily recognizable such as the corner of building, gate pillars, fence post, boundary stone
etc. Exact location of a reference point should be marked by dab of point or by a nail.

Fence post Corner of building

5.34
m
A
4.23m

3.78m
Gate
Figure: Location Sketch of Station ‘A’

Selection of Station
To locate the best position of survey stations, the surveyor should endeavor to meet the
following requirements:
1. Survey lines should be as few as practicable.
2. Survey lines should run over level ground.
3. Survey stations must be inter-visible.
4. Triangles should be well conditioned, and angles less than 30° should be avoided, if
possible.
5. There should be at least one base line that runs through the middle of the area. If two
base lines are used, they must intersect in the form of letter X.
6. As far as possible, the survey lines should be selected avoiding obstacles to ranging and
chaining, steep and uneven slopes.
7. Each triangle should have at least one check line to check the accuracy of field work. If
check lines can be used to pick up some details, so much the better.
8. Offset should be kept short especially to important features as the survey of a lot of long
tie-line is wasteful of time.
9. The main survey lines should remain within the boundaries of the area to be surveyed to
avoid trespassing.
10. Lines should be laid on one side of the road to avoid interruption to chaining by moving
traffic.
11. The sides of the larger triangle should pass as close and parallel to boundaries, roads,
buildings etc to have short offset.
12. Tie lines should be provided to locate details and to avoid too long offsets.

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 Surveying I: 3 Chain Surveying: IOE class notes 2011, compiled by: Vishwa Nath Khanal

13. While selecting the main stations and survey lines, the basic principle of surveying viz.
working from whole to the part and not from part to the whole should be followed. The
larger framework consisting of control triangles should be accurately surveyed first to fix
control points. The smaller triangles can then be fitted within the larger triangles, if
necessary.
Field Book and Booking Method: The note book in which chainages, offset measurements,
and sketches of detail points are recorded is called a field book. The art of recording
measurements in field book is known as booking. In general, single line field book and
double line field book are in use. Each page is is ruled up the center with either a single
colored line or with two such lines about 1.5 to 2cm apart to represent the chain line.
All the distances along the chain lines are written on the ruled red line in a single line field
book and between the two ruled lines in double line field book. To have correct orientation
of offsets, the measurement of the offsets are written either to the left or right of the
chainage line depending upon whether the detail lies to the left or right of the surveyor as
he walks along the chain line in the direction of the progress of the work. All the
measurements of chain line are taken from the chain line not from another detail.
The booking in the field book begins from the bottom of the page and proceeds towards the
top of the page. The booking of each survey line is started from the bottom of a fresh page.
The chainage of the starting station is zero. Sketches of detail points should be entered
neatly including required explanatory matter. All the measurements should be recorded in
the field book nothing should be left to memory. When any feature such as road crosses the
survey line, the chainage of the crossing point should be recorded. Extreme care should be
taken while recording the field measurements. The first page of the field book should
contain the following entries:
1. Title of the survey and location.
2. Date of survey and name of surveyors.
3. Reference sketch of the framework of triangles with letters or numbers.
4. Location sketch of the survey stations.
5. Page index of survey lines.
6. Details of survey lines like Name of the line and its length.
At the starting of a survey line, the following information should be recorded in the field
book:
a. Name of the survey line (eg., AB).
b. Name of the station marked either by a triangle or by a circle.
c. Bearing of the line (if measured).
d. Details of any other line meeting at the starting point of the survey line.

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 Surveying I: 3 Chain Surveying: IOE class notes 2011, compiled by: Vishwa Nath Khanal

Line BP Line BL
300 m

257 m
21 m

250 m 22 m building

232 m 27 m

32.5 m 187 m
El. pole

100.0

80.0 20 m road

to D
to B

A 0.00 m

Line0.00m
AC begins

A good field book is one which can be understood and drawn up by a person who has not
visited the site. Hence, a good field book should be accurate, neat and clear, and complete
with all necessary information for plotting the survey by a draught-person in the office.

Errors and their effects

Error is the difference between a measured value and the true value. Some error always
creeps in the measured quantities, and true value is never known. However, the most
probable value which is close to the true value can be determined by using the theory of
probability.
The surveyor must have the skill to make reasonably accurate measurements so that the
errors are within the permissible limit. The maximum allowable limit that a measurement
may vary from the true value is called the permissible limit. For some classes of work, an
error of one meter in a hundred does not matter, but for others (e.g., base line
measurement of a geodetic triangulation) an error of 0.1m in 1 km would be considered
excessive.
The method of measurement must be suited to accuracy desired. Great accuracy in linear
measurement is seldom necessary in ordinary engineering work. Careful measurement with
a reliable chain in good condition can give an accuracy of 1 in 2000, but it is best to recon
(rely) on 1 in 500 in normal practice, and perhaps a value as low as 1 in 200 if the
measurement is done rapidly over rough ground.

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 Surveying I: 3 Chain Surveying: IOE class notes 2011, compiled by: Vishwa Nath Khanal

A thorough knowledge of different types of error, their sources, characteristics and behavior
is essential for good surveyor. It would help him in selecting suitable methods and
techniques to achieve the desired accuracy. The errors that generally occur in chaining are:
1. Mistake: Mistakes are errors that arise from the inexperience, carelessness, and poor
judgment of the observer. Mistake produces serious effect in plotting and may lead to a
faulty plan. Generally committed mistakes are follows:
 Adding or omitting a full chain length in booking.
 Errneous booking i.e., both recording and calling numbers wrongly.
 Misreading the chainage by confusing the tallies.
 Failure to observe the zero point of the tape.
2. Systematic or cumulative error: A systematic error arises due to use of defective or faulty
instrument and always will have the same sign and magnitude under the same
conditions. Systematic error can always be corrected when their effects are detected or
known. If uncorrected, such error could have serious effect.
Correct length of line = Measured length of line [length of chain used ÷ length of standard]
Cumulative errors are caused in the following situations:
 Incorrect chain length
 Fluctuation in temperature
3. Random or accidental or compensating error: All those discrepancies which remain after
the correction of mistakes and systematic errors are known as random errors. Random
errors arise from lack of perfection in eye judgment and in the method of using
equipment, and act independently on observations. Random errors are caused in the
following situations:
 Incorrect holding of the chain
 Non-uniform calibration of chain throughout its length.
If the marking arrow is hold in an inclined position, the length of the arrow from which the
next chain length is to be measured will be either in front of or behind the actual end of the
chain. The errors from these sources tend to be cancel out i.e., tend to be compensatory.
These errors cannot be corrected as the nature of the error cannot be ascertained.

Degree of precision in measuring offset

Before commencing the field measurement, surveyor should know the degree of precision
to be maintained in measuring the length of offsets. This mainly depends on the scale of the
survey. A good draught-person can plot a fine point of 0.25mm on the paper. Therefore the
limit of precision in plotting is 0.25mm. Depending upon the scale of plotting, 0.25mm on
paper will correspond to:
0.25 x 100 = 25mm for scale 1: 100
0.25 x 200 = 50mm for scale 1: 200
0.25 x 500 = 125mm for scale 1: 500
0.25 x 1000 = 250mm for scale 1: 1000

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 Surveying I: 3 Chain Surveying: IOE class notes 2011, compiled by: Vishwa Nath Khanal

The allowable length (i.e., limiting length) of offsets depend upon the degree of accuracy
desired, scale of plotting, method of setting out the perpendicular, and nature of the
ground.

Effect of error in laying out the direction (perpendicular)

P1
P2 P

A C D B

 Consider the offset CP to be laid out from a point on the chain line.
 Let α be the angle of deviation i.e., error in laying perpendicular.
 Let length of CP be l. D be the foot of perpendicular from P on the chain line.
 ˂ PCD = 90° - α
 When the offset is plotted, the object P is displaced to P1 due to error in laying
perpendicular.
 The amount of displacement, PP2 = l Sin α
 Displacement of the point P perpendicular to the chain line, P1P2 = CP1 – CP2 = l - l Cos α

Possible obstacles and methods of overcoming them

Obstacles create difficulties to run the chain in straight direction between two points.
Depending upon the type of obstacles (eg.a small pond, standing crops, a small wood in the
middle, a river, and a rise of ground i.e., a small hill etc) a suitable method of indirect
measurement has to be chosen.
Obstacles in chaining: Chaining round the obstacle is possible.
C D C C

Pond
Pond
Pond
A B A B A B
Setout equal perpendicular AC & AB Setout AC perpendicular to AB
Measure CD, Then CD = AB Measure AC and BC AB = √[(BC)2 + (AC)2]
AB = √[(BC)2 - (AC)2]
A B

Select any point P. Range C in line with AP making AP = PC.

Range D in line with BP making BP = PD.
P Measure CD, then AB = CD
D C

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 Surveying I: 3 Chain Surveying: IOE class notes 2011, compiled by: Vishwa Nath Khanal

Obstacles in chaining: Chaining round the obstacle is not possible.

C
E
River D
Erect perpendicular BC & bisect it at D
Erect perpendicular CE & range E in line with
AD,
A B Then, AB = AC

C
River
C

B E
A

A D B ∟C = 90°, BC= BD,

Erect perpendicular at D,
Δ ADC & Δ BDC are similar, AD ÷ DC = DC ÷ DB
AB = BE D
Therefore, AD = (DC) 2 ÷ DB,

.
Obstacles in ranging: Both ends of the line visible from intermediate points

C D
B
A C1
D1

D2

C2
D3

A C3 D4 B

Figure: Reciprocal ranging

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 Surveying I: 3 Chain Surveying: IOE class notes 2011, compiled by: Vishwa Nath Khanal

Obstacles in ranging: Both ends of the line not visible from intermediate points

B1
D1
C1

A C D B
 A and B are not visible from intermediate point. Through A draw a random line AB 1 in any
convenient direction as nearly towards B as possible.
 B 1 should be so chosen that B 1 is visible from B, and BB 1 perpendicular to random line A B 1.
 Select C 1 and D 1 on random line and erect perpendicular to CC 1 and DD 1.
 Make CC 1 = (AC 1 ÷ AB1) BB 1, Because [CC 1 ÷ BB1 = AC 1 ÷ AB1]
 Make DD 1 = (AD 1 ÷ AB1) BB 1 , Because [CC 1 ÷ BB1 = AC 1 ÷ AB1]. Join CD and extend it.

Obstacles to both chaining and ranging

A building across the chain line is an example of obstacles to both chaining and ranging. If a
building is across the chain line, it would not be possible to range across the building and
continue chaining.
F E G H

Building
Building

C A B D

Select two points A and C before obstacles.

Erect perpendicular AE and CF of equal lengths. Check AF = CE.
Join F and E, and extend FE to point G and H beyond the obstacle.
Erect perpendicular GB and HD such that GB = HD = AE.
Join B and D. Line BD is the extension of chain line CA.
Obviously AB = EG.

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 Surveying I: 3 Chain Surveying: IOE class notes 2011, compiled by: Vishwa Nath Khanal

A D
D B C

C F E G

FD = FA
H K
B A G E
F
DE= DB, DF = DC, AG = CF

F H

A E
J

G K

Method of Plotting and Conventional Symbol

The main object of plotting is to produce drawings (plans or maps) of the area to be
surveyed. Preparation of plans or maps with the help of field notes is known as plotting. The
size of drawing paper can be determined by knowing the scale to be used and the area or
length of the survey. The plotting of a survey on the drawing paper must be oriented in such
a way that the north of the survey lies on the top of the sheet. The drawing paper may be
marked up with a grid of squares of suitable size having regard to the scale and then the
control points are first plotted.
The longest of the survey line (base line) is first drawn in the appropriate position and the
length is scaled. By striking arc with the help of beam compass other station are marked and
the network of the triangles are drawn. The triangles are then checked by drawing the check
lines measured in the field. If the error is within permissible limit it can be adjusted. The
sides of the affected triangles should be adjusted so that the check lines fit in accurately.
It is advisable to first plot the survey lines on a tracing paper and rotate the tracing paper on
the drawing paper so that the framework of the triangles is centered and oriented properly.
After obtaining the best orientation, the position of the ends of the base line are pricked
through the tracing paper on the drawing paper with a sharp pin. The points are thus
transferred from the tracing paper to the drawing paper. The tracing paper is then removed
and the base line is drawn on the drawing paper by joining the end points obtained after
pricking.
Once the network of triangles are plotted and checked, the features can be plotted. Offsets
are plotted systematically in the same order as they were booked i.e., working from
beginning to end for each line. The right angle for offset may be set out with a T-square and
set-square. When the points are plotted, the detailed features are drawn using the proper
conventional symbols. After completion of plotting work, the plan should be taken to the
site and be verified.

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 Surveying I: 3 Chain Surveying: IOE class notes 2011, compiled by: Vishwa Nath Khanal

The draught person should be careful against making simple mistakes like i. Plotting offsets
at the wrong point or on the wrong side of the line, ii. Omitting offset, iii. Scaling chainages
from wrong end of the chain line, iv. Joining wrong detail point.
Good quality drawing paper should be used for all important plans. Fairly hard pencils should
be used, as they make fine sharp lines, but they should not be so hard as to cut the paper.
Softer pencils may be used for lettering and offsets.
After completing the pencil work, the plan is sometimes inked with black ink for most or all
of the features with the exception of the chain lines which are shown in red ink. The offsets
and tie lines are not shown on the final drawing.
The north point must be shown on the plan, preferably at the top of the drawing sheet. The
scale of the plan should be drawn under the title.

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