A dumpy level is set up with its eye-piece vertically over a peg A. The height from the top of peg A to the centre of the eye-piece is 1.540 m and the reading on peg B is 0.705 m. The level is then setup over B. The height of the eye-piece above peg B is 1.490 m and a reading on A is 2.195 m. The difference in level between A and B is

ANS:C - 0.770 m

1. 1.540 m - 0.705 m = 0.835 m.
2. 2.195 m - 1.490 m = 0.705 m.
Now,
Difference in level between A and B = (0.835 + 0.705)/2.
= 0.770 m. Apply reciprocal leveling formula. Dividing 2 is done to eliminate error due to curvature and refraction. Average is taken to eliminate an error. Because if there was no error then 0.835 m and 0.705 m would be equal.