Question

Two distance 200 m and 298 m are measured from tacheometer instrument and corresponding staff intercepts are 2 m and 3 m respectively. Additive constant will be:
1. 2
2. 4
3. 98
4. 1

Answer 1

Correct Answer - Option 2 : 4

Concept:

According to principal of stadia method if line of sight is horizontal and staff is held vertical then horizontal distance between vertical axis of instrument and staff station is given by tacheometric distance equation.

D = kS + c

In this equation, Additive constant (c) and Multiplying constant (k)

Calculation:

Given:

D₁ = 200 m, D₂ = 298 m

S₁ = 2 m, S₂ = 3 m

200 = k × 2 + c    ….. Eq. 1

298 = k × 3 + c    ….. Eq. 2

From equations 2 and 3, the value of k = 98 and c = 4