Measurement of Vertical Angle

Horizontal sight is taken as zero vertical angle. Angle of elevations are noted down as +ve angles and angle of depression as -ve angles.

The following procedure may be followed to measure vertical angle:

1. At the required station complete all temporary adjustment.
2. Take up levelling of the instrument with respect to altitude level which provided on the A - frame.This levelling procedure is similar to that used for levelling dumpy level for example first altitude level is kept parallel to any 2 levelling screws and operating those 2 screws bubble is brought to centre. Then, level tube is brought at right angles by rotating telescope to the original position and is levelled with the third screw. The procedure is repeated until bubble is centred in both positions.
3. Then loosen the vertical circle clamp, bisect P & lock the clamp. Read verniers C and D to obtain vertical angle. Take the average as the exact vertical angle.