Chain Surveying | Principles, Types, Tape, Equipment & Important Points
📌 Introduction
Surveying is the science of measuring land, distances, and boundaries. Chain Surveying is the simplest and oldest method of surveying in which a chain (Zarib) or tape is used for linear measurements. It is suitable for small, open, and fairly level areas.
🔹 What is a Chain (Zarib)?
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A chain is an instrument used to measure linear distances.
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It is made of galvanized mild steel wire links connected together.
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Brass handles are fixed at both ends.
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Mainly used in small-scale surveys.
🔹 What is a Tape?
A tape is also used for linear measurements but is lighter and more accurate than a chain. Unlike a chain, it has no links.
Types of Tapes:
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Cotton Tape
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Metallic Tape
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Steel Tape
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Invar Tape
🔹 Principles of Chain Surveying
Chain surveying is based on 6 important principles:
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Linear Measurement: All measurements are linear and taken on a horizontal plane.
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Framework: The survey area is divided into a network of connected triangles, which should be well-shaped.
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Work Progress: The work should proceed from the boundary towards the interior.
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North Direction: The north direction of the area must be known before plotting.
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New Points: Any new point must be fixed by observation from at least two known points.
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Offsets: Features away from the survey line are located using offsets (preferably perpendicular).
🔹 Types of Chains
Type of Chain | Length | Number of Links | Special Use |
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Engineering Chain | 100 ft | 100 | 1 link = 1 ft, engineering works |
Gunter’s Chain (Surveyor’s Chain) | 66 ft | 100 | 1 link = 0.66 ft, land measurement |
Revenue Chain (Patwari Chain) | 33 ft | 16 | Used in land & agricultural surveys |
Metric Chain | 5m, 10m, 20m, 30m | 25, 50, 100, 150 | 1 link = 20 cm, modern surveys |
Steel Band (Tape Chain) | 20m, 30m | Continuous markings | Steel strip, high accuracy |
🔹 Equipment Required for Chain Survey
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Chain
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Tape
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Arrows (Marking Pins)
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Ranging Rods
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Offset Rod
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Peg & Mallet
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Plumb Bob
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Flags
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Line Ranger
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Optical Square / Cross Staff
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Field Book
🔹 Advantages of Chain Surveying
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Simple method
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Requires inexpensive instruments
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Quick execution
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Suitable for small and level areas
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Useful for boundary marking and large-scale maps
🔹 Limitations
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Not suitable for large or hilly areas
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Only linear measurements possible (no angular measurement)
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Less accurate than modern methods
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Obstacles like rivers, trees, buildings cause difficulties
🔹 Checking & Adjustment of Chain
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Chain length is checked against a standard chain or standard tape.
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To reduce increased length: close open rings, replace large rings with smaller ones, adjust near handles.
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To increase reduced length: straighten bent links, replace small rings with larger ones, add new rings if required.
🔑 Important Points (Exam-Oriented Quick Notes)
Basic
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Chain = Instrument for linear measurement.
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Tape = Lighter & more accurate than chain.
Features
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Only linear measurement is taken.
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Best for small, plain, and open areas.
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Not used where high accuracy is required.
Principles (6)
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Measurements must be linear & horizontal.
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Triangular framework.
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Progress from boundary inward.
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North direction must be known.
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New points from two known points.
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Use offsets for side features.
Types of Chains
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Engineering Chain = 100 ft (100 links)
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Gunter’s Chain = 66 ft (100 links)
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Revenue Chain = 33 ft (16 links)
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Metric Chain = 5m, 10m, 20m, 30m (link = 20 cm)
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Steel Band = 20m/30m steel strip
Types of Tapes
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Cotton, Metallic, Steel, Invar
Equipment
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Chain, Tape, Arrows, Ranging Rods, Offset Rod, Peg & Mallet, Plumb Bob, Flags, Line Ranger, Optical Square, Field Book
Advantages
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Simple, cheap, quick, easy to use
Limitations
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Only for small, level ground
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Not suitable for precision work
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Obstacles create errors
Frequently Asked Exam Questions
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How many principles of chain surveying? → 6
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Length of Gunter’s Chain? → 66 ft
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Revenue chain is also called? → Patwari’s Chain
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Length of 1 link in Metric Chain? → 20 cm
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Why Invar Tape is used? → Very low thermal expansion
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