Chains could be divided into following 5 types as per units of measurement
- Metric chain
- Revenue chain
- Gunter’s chain
- Engineers chain
- Steel band
Metric chains are the most widely used in India for linear measurement. These chains are available in 10m, 15m, and 30m length. In this type of chains length of 1 link is 20cm.
Metric chains are made from galvanized mild steel of 4 mm thick wire. Metric chains are bent into a loop at the end and connected with each other by means of three circular rings.
Metric chain comes with brass rings at every one meters interval. It also has brass tally at every 5 meters interval.
Revenue chains are 33 feet long consisting 16 links. And thus, this chain is used for work of measuring small area.
Gunter’s chain or Surveyor’s chain
These chains are 66 feet in length consisting 100 links each of 0.66 ft. Here, it is worth to note that area covered by square made up of length and width equals to 10 chain is being equal to 1 acre.
10 chains = 1 furlong and 8 Furlong (80 chains) = 1mile
Engineers chain is 100 feet long comprising 100 links each of 1 foot. This chain is also used to measure length in foot and inches.
Steel Band and Band Chain
Steel bands are more accurate than chain being available in 20m and 30m length. The major drawback is that they got easily broken while carrying from one place to another one. They are 12 to 16 mm in width and 0.3 to 0.6 in thickness.
Equipment used for chain surveying
Following are the essential instruments for chaining
- Ranging rods
For linear measurements, minimum three ranging rods are needed. Ranging rods are painted alternatively, from top to bottom, either red and white or black and white for better visibility.
This are used to mark a location on ground during surveying and are made from iron and having sharp nib.
They are made from wood and used to permanently mark a location.
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