Collimation Error

2.12 The observations listed below were recorded when testing the adjustment of an automatic level. Use them to calculate the collimation error in the level.

Level Position	Staff Reading	Sighting distance	Staff Reading
L1	A	25m	1.225m
L2	B	25m	1.090m
L3	A	55m	1.314m
L4	B	5m	1.155m

Expert Answer ^{♥♥♥ ‘} 

Problem 2.12

Instrument at I_1,                                                                                   Instrument at I_2,

True difference in level between A and B                                   Apparent level difference between A and B

= 1.225 – 1.090                                                                                 = 1.314 – 1.155

= 0.135m A is lower                                                                          = 0.159m A is lower

Therefore, connecting reading at A        = Reading at B + 0.135

= 1.155 + 0.135     = 1.290m

Observed reading at A   = 1.314m

1.314m > 1.290, the line of collimation is upward elevated,

Collimation Error

C’ error in 50m, = 1.314 – 1.290 = 0.024m

C’ error in 55m, = 0.024 x   = 0.0264m