Equipment Used for Chain Surveying

Chain surveying is a method of surveying which involves the linear measurement of survey distance. It works based on the principle of Triangulation. The major instruments used for chain surveying is measuring chain.

Equipment Used for Chain Surveying

The various instruments that are used to determine the length of line by chaining are:
  1. Chain
  2. Tape
  3. Arrows
  4. Pegs
  5. Ranging Rods
  6. Mallet
  7. Cross Staff

1. Chains in Surveying

Chains are made of galvanized mild steel wires in the form of straight links. The straight links are bent to form rings at the end and they are joined by circular or small wire rings as shown in the figure below.
chains in surveying
Figure-1. Chains in Chain Surveying

The three rings provided after each straight link as shown in the figure provide flexibility to the chain. In order to have better handling of chain, brass handles are provided at the ends as shown above, with a swivel joint. This arrangement of handle can turn the chain as required, without twisting.

The length of one link is the centre to centre distance between two consecutive middle rings as shown in figure-1 above. The length of the chain is measured as the distance from left most end of handle to right most end of handle.

The major types of chains are:
  1. Metric Chains
  2. Gunter's Chain or Surveyor's Chain
  3. Engineer's Chain
  4. Revenue Chain
  5. Steel Band or Band Chain

2. Tapes in Surveying

Tapes are used for accurate measurement of distances. The major types of tapes used in surveying are:
  1. Linen Tape
  2. Metallic Tape
  3. Steel Tape
  4. Invar Tape

3. Arrows in Chain Surveying

Arrows are also called as chaining pins. These are used to mark the end of a chain during the chaining process. Arrows are pointed at one end that is used to pierce into the ground and the other end is a circular ring for the ease of carrying as shown in figure below.

Arrows used in Chain Surveying.
Figure-2. Arrows used in Chain Surveying.

Arrows are made of hardened and tempered steel wire of diameter 4mm. The length of an arrow is 25 to 50 cm. 

4. Pegs in Chain Surveying

Pegs are made out of timber as shown below with a cross-section of 2.5 x 2.5 or 3 x 3 cm. It has a length of 15cm, with flat end at one side and pointed at the other end. Wooden pegs are used to mark the positions of stations or terminal points of a survey line.

Figure-3. Wooden Pegs in Chain Surveying

5. Ranging Rods

Ranging rods are rods with length of 2m, 3m or 4m with a circular cross-section of 30 mm in diameter. These rods are provided with a iron shoe at the bottom and are painted red , black and white bands of 20 cm. It can be used for rough measurements of short length when necessary. For long distance ranging, we can make use of flags at the end. 

Figure-4: Ranging Rods

6. Offset Rods in Chain Surveying

Offset rods are used to locate the measuring offsets. It is 3 m long that is made of seasoned wood and graduated in meters. One meter at each end is subdivided into alternate black and white bands of 5 cm each.
Figure-5: Offset Road

7. Mallet

Wooden mallets are used for driving the wooden pegs into the ground.

8. Cross-Staff

A cross staff is an instrument that provides one pair of line of sight perpendicular to each other. It is used:
  1. To set out a line at right angles to a chain line at any point lying on it
  2. To locate the foot of the perpendicular on a chain line from a point lying outside.

Figure-6: Cross-Staff

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