The following readings were obtained during differential levelling. The reduced Level (RL) of point A is 240.000 m. The foresight and back sight between points A and TPI is 1.420 m and 2.024 m, respectively.

The following readings were obtained during differential levelling. The reduced Level (RL) of point A is 240.000 m. The foresight and back sight between points A and TPI is 1.420 m and 2.024 m, respectively. Fore sight and back sight between points TP1 and TP2 is 2.100 m and 1.986 m, respectively. The back sight from B is 1.722 m. These are marked on the given figure. What is the RL at turning point-2 (TP2)? All values are in meters.

Right Answer is:

240.490 m

SOLUTION

The operation of levelling to determine the elevation of points at some distance apart is called differential levelling and is usually accomplished by direct levelling.

Start with A (+ve for up and –ve for down)

Elevation of TP2 compare to A

= +2.024 + (1.986 – 1.42) – 2.1

= + 0.49

∴ RL of TP2 = 240 + 0.49 = 240.49 m

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