A theodolite is set up at station A. The RL of instrument axis is 212.250 {m}. The angle of elevation to the top of a 4 {m} long staff, held vertical at station {B}, is 7^{\circ}. The horizontal distance between stations A and B is 400 {m}. Neglecting the errors due to curvature of earth and refraction, the {RL} (in {m}, round off to three decimal places) of station {B} is _________

GATE Civil Engineering (CE) 2020 Shift 2 Solved Paper

Question : 59 of 65

Marks: +1, -0

A theodolite is set up at station

A

. The RL of instrument axis is

212.250 {m}

. The angle of elevation to the top of a

4 {m}

long staff, held vertical at station

{B}

, is

7^{∘}

. The horizontal distance between stations

A

and

B

400 {m}

. Neglecting the errors due to curvature of earth and refraction, the

{RL}

(in

{m}

, round off to three decimal places) of station

{B}

is _________

Solution:

\;{ {PQ}}/{400}=\tan 7^{∘}

{PQ}=49.113

{RL}

{B}=212.250+49.113-4

=257.363 {m}

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