Errors in measurement due to incorrect length of chain

• The length of a chain may be correct at the beginning, but it may change with time as more and more used. Due to continuous use of the chain over rough ground, the oval shaped rings get elongated and thus the length of the chain increases.
• On the other hand some of the links may get bent for there may be kinks. As a result the chain length reduces. In a very old chain, some ring or links may be missing. Therefore, before the start of the work the correctness of the chain length should be tested with a steel or invar tape.
• If the chain is too long, measured distance will be less and if the chain is short, the measured distance will be more than the actual distance. However, the measured distance can be corrected by using the formula:

Correct distance = (  ’/   ) × Measured distance

Where L’= incorrect length of a chain,

L = normal correct length of a chain which may be 20m, 30m,etc.

Therefore, correct distance × correct length of chain= Incorrect distance × incorrect length of chain.=

If e is elongation or shortening of chain length, L’= (L+ e), plus sign is used when the chain is too long and minus sign is used when the chain is too short.

(iii) always to carry the rear handle in his hand and not to allow it to drag on the ground, and

(iv) to pick up the arrows inserted by the leader. The chainman who is more intelligent and experienced be selected as the follower, as upon his care and judgment, depends the accuracy of measurements.