The readings obtained from a two-peg test carried..
2.1 The readings obtained from a two-peg test carried out on an automatic level with a staff placed on two pegs A and B 50 m apart are:
- With the level midway between A and B
Staff reading at A = 1.283 m Staff reading at B = 0.860 m
- With the level positioned 5 m from peg B on line AB extended
Staff reading at A = 1.612 m Staff reading at B = 1.219 m
Calculate the collimation error of the level per 50 m sighting distance and the horizontal reading that should be observed on the staff at A with the level in position 5 m from B.
Expert Answer ♥♥♥
S1 = 0.860 m S2 = 1.283 m S3 = 1.219 m S4 = 1.612 m
From Equation of collimation error e = (S1-S2) – (S3-S4) per L m
e = (0.860 – 1.283) – (1.219 – 1.612) per 50m
= (-0.423-(-0.393)) = -0.030m per 50m
For the instrument in position 5 m from peg B, the horizontal reading that should have been obtained with the staff at A is
S’4 = S4 – [Collimation error per meter x sighting distance DA]
= 1.612 – 55 = 1.645m
This is checked by computing S’3, where
