A chain survey is a particular type of survey method in which only linear measurement is taken. Linear measurements are taken in the field.
Angular measurements are not taken in chain surveying.
Chain surveying is also called chain triangulation.
Chain surveying is used when the area is small. It is not feasible for a large area. Chain surveying is done to define the boundary and its features for a small land area or plot. A land surveyor can define the features of the plot on the surface of the land.
In this type of surveying, the whole area is divided into small triangles. The sides of triangles can be measured by using a tap or chain. Only linear measurements can be taken. Length and width are considered linear measurements. Angular measurement is not possible by using chain surveying.
Triangles should be well-conditioned. Well-conditioned triangles follow specific conditions. All the angles in well-conditioned triangles should be more than 30° and less than 120°.
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Chain Surveying Principal
Two important things are considered for chain surveying.
- The whole plot area is divided into various small triangles. All the triangles should be well-conditioned triangles.
- Linear measurements are taken of the triangles.
As we have stated earlier, all the angles should be well-conditioned. For well-conditioned triangles, the angles between two sides of the angle vary between 30° to 120°.
It is much easier for land surveyors to take measurements of equilateral triangles.
Equipment for Chain Survey
Instruments used in chain surveying are as follows.
- Chains
- Taps
- Ranging rods
- Ranging poles
- Pegs
- Arrows
- Laths
- Whites
- Plumb bob
Types of Chain
Normally five types of chains are used for chain surveying.
- Metric chain
- Gunter’s chain
- Engineer’s chain
- Revenue chain
- Steel band
1. Metric Chain
Metric chains are available in the market for various lengths such as 5 meters, 10 meters, 20 meters, 30 meters, etc. The link of the metric chain is made of galvanized iron. The diameter of galvanized mild steel wire is 4 meters. Both ends of the chain are fitted with a brass handle. Brass handles are fitted with swivel joints.
Swivel joints are provided to prevent moments and to avoid jumbled up.
2. Gunter’s Chain
This type of chain is also called the surveyor’s chain. The total length of the gunter’s chain is 6 feet. It is made of a total of 100 links. The length of one link is 0.66 feet. Gunter’s chain is more useful when the length is measured in feet and the area is measured in acres.
3. Engineer’s Chain
The length of the engineer’s chain is 100 feet. It consists of 100 links. The length of each link is 1 foot. It is used where length is measured in feet and area is measured in square yards.
4. Revenue Chain
The revenue chain is normally used for cadastral surveys. It is 33 feet long. This type of chain consists of 16 links.
5. Steel Band
As the name suggests it is a ribbon made of steel. Brass handles are attached at both ends of the handles. It is attached by swivel joints. Normally it comes in 20 meters and 30-meter lengths.
The steel band is 12 mm to 16 mm wide and 0.3 mm to 0.6 mm thick.
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