Chaining: The process of measuring distance with the help of chain and tape is called Chaining Process. It is most accurate method for linear measurements. The instruments used in Chaining process are:
1.Chain
It is composed of a definite numbers of links made up of galvanised mild steel wire 4mm dia. The end of links are bent into loop and these loop are connected with each other by three circular rings to make chain flexible. There are different type of chains are:
1a. Metric Chain:
a. 20 meter chain- 100 links
b. 30 meter chain- 150 links
2b. Non Metric Chain:
a. Engineer Chain (100 feet)- 100 links
b. Gunter Chain (66 feet)- 100 links
2.Arrows
These are also known as Marking or chaining Pins used to mark the end point of chain during linear measurements process. It is 40 cm long and a ring at one end made up of a steel wire 4mm in dia.
3.Tapes
It is used in linear measurement where more accuracy is required. It work is similar to chain execpt taking reading on tape is quite easy.
a.Linen or Colth Tape b.Metallic Tape
c.Steel Tape d.Invar Tape
c.Steel Tape d.Invar Tape
4.Ranging Rods
The rod made of straight, light bamboo, well seasoned wood or steel pipe having diameter 3 cm and length 2-3 m. A square flag of 25 cm are placed at top of rods. It is used for marking position of stations and in ranging of lines. The rods are painted either in striped form of white and red or in white and black colour.
5.Offset Rod
It is similar to Ranging Rods except flag on top. It is used to taking offsets of any structures.
6.Pegs
The wooden rod of length varies from 15 cm to 60 cm are tapered at one end. It is used to mark the station on ground.
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