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A theodolite is set up at station A and a 3 m long staff is held vertically at station B. The depression angle reading at 2.5 m marking on the staff is 6°10'. The horizontal distance between A and B is 2200 m. Height of instrument at station A is 1.1 m and R.L. of A is 880.88 m. Apply the curvature and refraction correction, and determine the R.L. of B (in m).
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- 212.205 m
- 642.205 m
- 342.65 m
- None of the above
Correct Option: B
R.L. of A = 880.88 m
R.L. of Plane of Collimation = 880.88 + 1.2 = 882.08m
True staff reading at station B = 2.5 – 0.0673 × 2.22 = 2.174 m
Now, B'B'' = (tan6º 10') × 2200 = 237.701 m
R.L. of station B = R.L. of Plane of Collimation – true staff reading – B'B''
= 882.08 – 2.174 – 237.701 = 642.205 m
