Height of Instrument Method | Surveying and Levelling

Height of the Instrument Method

The following readings were observed with a levelling instrument, the instrument was shifted after 5^th and 11^th reading.

0.585, 1.010, 1.735, 3.295, 3.775(5^th)

0.350, 1.300, 1.795, 2.575, 3.375

3.895 (11^th), 1.735, 0.635, 1.605

Determine the RLs of various points if the reduced level (RL) of a point on which the first reading was taken is 136.440 gives the height of collimation method and applies the check.

Station	BS	IS	FS	HI	RL	Remarks
123 4 5	0.585    0.350	1.0101.735 3.295	3.775	137.025    133.600	136.440136.015135.290 133.730 133.250	RL of I point    CPI
678 9 10	1.735	1.3001.7952.575 3.375	3.895	131.440	132.300 131.805 131.025 130.225 129.705	CP II
1112		0.635	1.605		130.805 129.835
	Sum of BS=2.670		Sum of FS =9.275

HL = RL + BS

= 136.440 + 0.585

= 137.025

RL = HL – IS

Check

(Summation of BS)-(Summation of FS) = Last RL – First RL

2.670 – 9.275 = 129.835 – 136.440

-6.605 = -6.605