How to calculate constants of tacheometer ?/ Finding tacheometer constants in surveying.

 Eg: Calculate tacheometer constants for the following observations on site.

Instrument Station	Staff position	Distance	Staff reading
P	A	50	1.425	0.930
	B	150	2.250	0.765

 

Calculation:

Find:

Multiplying constant f /i (or k) =?

Additive constant f +d ( or C) =?

The formula used in tacheometric survey are

D = KS + C

     or

D = (f/i ) S + (f +d)

For distance PA

D1 = (f/i ) S1 + (f +d)

Here,

D1 = 50m. (given)

S1 = [1.425 - 0.930]

     = 0.495

50m. = (f/i ) 0.495 + (f +d) --------------- ①

For distance PB

D2 = (f/i ) S2 + (f +d)

Here,

D2 = 150m. (given)

S2 = [2.250 - 0.765]

     = 1.485

150m = (f/i ) 1.485 + (f +d) --------------- ②

Subtracting equation ① from equation ②,

[150m - 50m.] = (f/i ) (1.485 - 0.495) + 0

100 = [(f/i ) × 0.99]

(f/i ) = [100 ÷ 0.99]

         = 101.01

Now, substituting the value of  (f/i ) in equation  ①

50m = (101.01 × 0.495) + (f +d)

(f +d) = 50m - 49.99995

          = 0.00005 ≈ 0.0

To understand A to Z of surveying, click here.

Thank you for going through these calculation steps❤. Have a good day 😄

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