Chain Surveying

Chain surveying is one of the simplest methods of surveying, used primarily for measuring linear distances on the ground with the help of a chain or tape. It is suitable for small, open, and fairly level areas, and is commonly used in civil engineering, land measurement, and agricultural surveying.

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History

The use of chains in surveying dates back to the early 17th century. The most notable development was the invention of Gunter’s chain by the English clergyman and mathematician Edmund Gunter in 1620.

• Gunter’s chain was 66 feet long and consisted of 100 links, each 0.66 feet in length.

• This design allowed easy conversion between measurements of area:

  • 10 square chains = 1 acre

  • 80 chains = 1 mile

• The chain became widely used in Britain and its colonies for land measurement, agricultural mapping, and revenue surveys.

• In India, the Revenue Chain (33 ft, also called Patwari’s chain) was introduced during the British colonial period for agricultural land surveys, a practice still followed in some regions.

With advancements in surveying technology, steel tapes, invar tapes, and electronic instruments gradually replaced the traditional chain, but chain surveying remains important in teaching, small-scale surveys, and historical land measurement studies.

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Overview

In chain surveying, the entire area to be surveyed is divided into a framework of interconnected triangles. Linear measurements are taken with the help of a chain, tape, or steel band. Angular measurements are not employed in this method, making it distinct from other types of surveying such as compass surveying or theodolite surveying.

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Principles

Chain surveying is based on the following fundamental principles:

1. All measurements are linear and taken on a horizontal plane.

2. The survey area should be divided into well-conditioned triangles.

3. Work should progress from the boundary towards the interior.

4. The north direction of the survey area must be known before plotting.

5. Any new point should be established by reference to at least two known points.

6. Features away from the survey line are located using offsets, preferably perpendicular.

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Types of Chains

Several types of chains are used in surveying:

• Engineering Chain: 100 ft long, consisting of 100 links, commonly used for engineering works.

• Gunter’s Chain (Surveyor’s Chain): 66 ft long, with 100 links, traditionally used for land measurement.

• Revenue Chain (Patwari Chain): 33 ft long, with 16 links, used for land and agricultural surveys.

• Metric Chain: Available in lengths of 5 m, 10 m, 20 m, and 30 m; one link is equal to 20 cm.

• Steel Band (Tape Chain): Made of a steel strip, available in 20 m and 30 m lengths, and used for high accuracy.

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Tapes

Tapes are also employed in place of chains for improved accuracy. Common types include:

• Cotton tape

• Metallic tape

• Steel tape

• Invar tape (noted for its very low coefficient of thermal expansion)

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Equipment Used

The instruments required in chain surveying include:

• Chain or tape

• Arrows (marking pins)

• Ranging rods

• Offset rod

• Peg and mallet

• Plumb bob

• Flags

• Line ranger

• Optical square or cross staff

• Field book

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Advantages

• Simple and easy to use

• Inexpensive instruments

• Quick execution for small areas

• Suitable for boundary marking and preparation of large-scale maps

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Limitations

• Applicable only to small, level, and open areas

• Not suitable for large-scale or hilly regions

• Obstacles such as rivers, buildings, or trees create difficulties

• Provides only linear measurements, without angular accuracy

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Applications

Chain surveying is primarily used in:

• Preparation of maps for small plots of land

• Agricultural and revenue surveys

• Boundary marking

• Preliminary site surveys for civil engineering works

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See Also

• Surveying

• Compass Surveying

• Theodolite Surveying

• Levelling (surveying)

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