(a) Describe the surveyor's chain (b) Outline any three problems that could be encountered in the use of the surveyor's chain.
Question 1 Report
(a) Describe the surveyor's chain
(b) Outline any three problems that could be encountered in the use of the surveyor's chain.
Answer Details
(a) The surveyor's chain
The surveyor's (Gunter's) chain is an instrument used for measuring horizontal distances on the ground during land survey. It is made up of 100 links of galvanised steel wire joined together by small rings, with a brass handle at each end. Its standard length is 66 feet (about 20.1 metres), so that each link is 7.92 inches long. Brass tags or markers are fixed at every 10 links to make counting easier, and it is used together with a set of metal arrows (pins) for marking the ends of each chain length and ranging poles for keeping the line straight.
(b) Three problems in using the surveyor's chain
- Sagging and stretching: the chain may sag in the middle or stretch after long use, giving inaccurate (usually too long) measurements.
- Difficulty on rough or sloping ground: hills, valleys, rivers, bushes and obstacles make it hard to lay the chain horizontally and straight, causing errors.
- It is slow and needs many people: chaining is tedious, requires at least two people (leader and follower), and mistakes in counting chains or arrows lead to errors.
Other problems include kinking or breaking of links, rusting of the steel, and errors from failing to keep the line truly straight.
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