Unit 2: Chain Surveying
25 November 08
Unit 2 :Chain Surveying
1
Topics covered
Different methods for linear measurement,
instruments for chaining
Different types of Chains/Tapes
Ranging - Direct, Indirect, chaining on sloping
ground
Chain surveying: survey station, survey line,
locating the ground features with the help of offsets.
Chain surveying, fieldwork & office work
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Unit 2 :Chain Surveying
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2.1 Linear measurement- Basics
Horizontal distance is correct
One of the basic function in
surveying
B
 Always horizontal not sloping
distance
 No way to check the error other
A
than remeasuring
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2.1 Linear measurement methods
Methods
Direct measurements
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By optical means
Unit 2 :Chain Surveying
Electronic methods
4
2.1 Direct measurements
Instruments such as
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Pacing
Passometer
Pedometer
Odometer or Speedometer
Rough methods for preliminary survey
Check of large mistakes in measurement made by more
precise method
Unsuitable in irregular and sloping ground
Precision – 1/50 to 1/200
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2.1 Taping / Chaining
Chaining or taping carries same meaning
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Use of either chain or tape.
One of the accurate method of direct measurements
This method is basis for most surveying.
Precision

1/1000 to 1/5000 (ordinary land survey)
Use of chain or tape
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Chain (Early 1600s)
Steel tape in use by early 2000s
Tape is very common nowadays.
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2.1 Instruments for chaining/taping
Chain/tape
Arrows
pegs
Ranging rods
Plumb bob
Hand level
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Unit 2 :Chain Surveying
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Contd….
2.1 Instruments for chaining/taping
Arrows
10 arrows

Pegs
Station position
 Terminal points of survey line

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2.1 Instruments for chaining/taping
Contd….
Ranging rods
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Used to range intermediate points on survey line
Length 2 m ( very common) or 3 m
Bands of 20 cm painted alternate colour( red & white, black &
white)
Ranging poles
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Similar to ranging rod but big in size
Used in case of long lines
Used to range intermediate points on survey line
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2.1 Instruments for chaining/taping
Contd….
Plumb bob
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Verticality of ranging pole
Transferring the points to ground
Also used for centring purpose in
other surveying methods.
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2.2 Different types of chain/tape
Chain (Absolute equipment at present)
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Metric chain (available in 5,10,20
meter)
Gunter’s or surveyor’s chain (66 ft of
100 links)
Engineer’s chain (100 ft of 100 links)
Revenue chain (33 ft of 16 links)
Steel band or band chain ( 20 or 30 m)
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2.2 Different types of chain/tape
Contd….
Tape
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Cloth or Lenin tape
Metallic tape
Steel tape
Invar tape (Alloy of nickel 36% & steel)
Cloth Tape
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Steel Tape
Linen Tape
Unit 2 :Chain Surveying
Metallic Tape
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2.3 Ranging
When the length of survey line is greater than chain or
tape length
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Process of establishing intermediate points
Methods
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Direct Ranging
Indirect Ranging
Intermediate points
> one tape length
B
A
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2.3 Direct ranging
Direct ranging
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When two end points are intervisible
Either by eye or through optical instruments such as
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Line ranger
Theodolite
Code of signals used to direct assistant
< one tape length
P
B
A
Transverse movement
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2.3 Indirect ranging
Indirect ranging
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When two end points are not intervisible
With the aid of two intermediate points very near to the line
M
N
A
B
M
A
N
M3
N3
B
M2
N2
N1
M1
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2.3 Chaining/taping over sloping
ground
Methods
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Direct method or method of stepping
Indirect method
 With the aid of vertical angle measurement
 With the aid of difference in level measurement
 Hypotenusal allowance
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2.3 Chaining/taping over sloping
ground
Contd….
Direct method or stepping method
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Convenient to proceed down-hill
Tape shall be horizontal
Sufficient pull to avoid sag
Lengths of steps inversely proportion to degree of slopes.
l1
A
l2
l3
l4
D = (l1+l2+l3+l4)
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2.3 Chaining/taping over sloping
ground
Contd….
Indirect method (Vertical angle measured)

Clinometer to measure vertical angle
A
D1 = s1×cosΦ1
The required horizontal distance (D) =∑s cosΦ
s1
Indirect method (difference in height)
Φ1

Level machine is used
to measure h to compute D.
D = √( s - h
2
2
D1
A
h
C
)
Indirect method (Hypotensual allowance)
s2
s
C
Φ2
B
D2
D
A
BA / = BC = 1 CHAIN
B
A’
BA = 1 CHAIN × sec θ
AA / = BA - BA /
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= 1 CHAIN ( sec θ – 1)
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C
θ
B
1 chain
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2.4 Chain surveying
What is chain surveying?
Principle of chain
surveying
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Triangulation
Survey stations
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Main station (A, B, C,…E)
Subsidiary stations (F, G, H)
Marking of stations
Survey lines
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Main survey lines
Base lines
Check lines
Tie lines
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2.4 Survey stations & survey lines
Station
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Mutually visible
Survey lines
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Few as far as possible
Must have one base line
Pass through level ground
Form well-conditioned triangle
Sufficient check line
Short offset
Should not pass through obstacle
Should fall within the boundaries
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2.4 Locating the ground features
Offsets- lateral distance of an object
from survey line.
Offsets should be as small as possible
Types
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Perpendicular – less measuring on ground
A
Oblique
Method of ties
900
B
C
P
P
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P
≠ 900
Q
A
Unit 2 :Chain Surveying
B
C
21
Contd….
2.4 Locating the ground features
Swing of the tape on chain
line
Shortest distance is
perpendicular offset
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P
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Contd….
2.4 Locating the ground features
Offsets are taken in the
order of their chaninage.
Number of offsets depends
upon the shape of objects
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Boundary wall
Straight wall, zigzag wall, road
with constant width
Constant width road
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Contd….
2.4 Locating the ground features
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2.5 Chain surveying (field/office work)
Equipment
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Chain/Tape (>30 m)
10 Arrows
Raging rods
A tape ( 10 m or 20 m )
Cross staff or Optical square
Field book, pencil
Plumb bob
Pegs, wooden hammer, chalks
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2.5 Field work
Field work consists of three steps
Reconnaissance
Marking and fixing survey stations
Running survey lines
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Reconnaissance
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Walkover survey with the view of principle of
surveying
Reference sketch
Thinking of possible problem and their solution
in actual survey
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Contd….
2.5 Field work
Purpose is to enable to locate stations
during progress of work
Wooden pegs in soft ground
Nails or spikes in hard surface (road) &
flushed with pavement
For a long time used station, a stone of
standard size fixed with mortar
Reference of two or three permanent
object
Building
Chaupari
9.90m
9.65m
10.50m
Electric pole
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2.5 Field work
Contd….
Start chaining from base line
Consists of two folds
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Chain the survey line
Locate the adjacent details
Chaupari
One tape length
Building
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2.5 Field work
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Contd….
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2.5 Office work
Part of office work
Computation of data
Plotting work
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Size of paper should be
standard (in mm)
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A0 = 840 * 1188
A1 = 594 * 840
A2 = 594 * 420
A3 = 420 * 297
A4 = 297 * 210
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2.5 Plotting work
Fix the scale of survey before
starting
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Purpose of survey
Extent of survey
Finance available
North upward rule
Nice lettering (Always in the
drawing)
Skeleton first then offsets
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Use of tracing paper for proper
orientation
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2.5 Plotting work
Start with base line
Triangles are laid by intersection of
arcs
Verification of check lines
Offsets are then plotted by
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Set square or
Offset scale
Ground features representation
with symbol
Title box and legend box
Use of HB, 2H and 3H pencils
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Conventional symbols
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Conventional symbols
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Contd….
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