This question was previously asked in

Gujarat Engineering Service 2019 Official Paper (Civil Part 1)

Option 1 : focal length of the objective lens divided by the distance between the stadia wires

CT 1: Current Affairs (Government Policies and Schemes)

54560

10 Questions
10 Marks
10 Mins

**Explanation:**

Tachometer: It’s a transit theodolite fitted with a stadia diaphragm which gives both horizontal and vertical control with an accuracy of 1 in 1000.

From the above figure, the horizontal distance is given by -

D = kS + C

This formula involves the computation of two constants i.e.** multiplying constant (k) and additive constant (c)**.

\(\rm{k = \frac{f}{i}\;{\rm{and\;}}c = f + d}\)

Where,

f = Focal length of the objective lens

i = Distance between the stadia wires

d = distance of the objective from the center of the instrument.