Best Study Material for Civil Engineering (CE) Exam
Arithmetic Check
Reciprocal LevellingHere, X = error due to inclined line of sight, and
e = error due to curvature and refraction
CC = -(d2/2R)
Here, d = horizontal distance between A and B
R = radius of earth
If R = 6370 km
Than CC = -0.07849d2
here ‘CC’ is in meter and ‘d’ is in kilometer
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Test: Levelling - 1
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Sensitiveness of the bubble tube is defined as the angular value of one division of the bubble tube.
α' = sensitivity of the bubble tube
= angular value of one division
α' = S/nD x 206265 seconds
Or α'= S/nDsin1" seconds
Here, S = difference between two staff readings.
n = no. of divisions of bubble
also, α' = l/R radian or α' = l/Rsin1" seconds
where, l = length of one division
R = radius of curvature of bubble tube.
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