Numerical Examples for Errors in Chain Surveying



A practical Example for Calculation of the True Area of the field | Errors in Chain Surveying

In my previous article, we studied how to measure true distance considering the Errors occurring in Surveying.

Correction formulas to be kept in mind (for incorrect length of Chain)

True distance = L’/L*measured distance

True area = (L’/L)2*measured area

True Volume = (L’/L)3 * measured volume

Where, L’ = incorrect length of chain

L = correct length of chain

The chain was tested before starting the surveying and was found to be 20m. At the end of surveying, it was tested again and was found to be 20.12m. The area of the plan of the field drawn to a scale 1cm = 6m was 50.4sqm. Find the true area of the field in sqcm.

Scale of the plan

1cm = 6m

1cm2 = 36m2

Area of plank = 50.4 cm2

Measured area of field = 50.4 * 36

= 1814.4m2

Incorrect length of chain, L’ = (20+20.12)/2

= 20.06m

L = 20m

True area = (L’/L)2 * measured area

= (20.06/20)2 * 1814.4

= 1825.3m2

1 hectare = 10,000m2

= 0.1825 hectare

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