Adjustment of Level
Temporary adjustments of Level
The temporary adjustments for a level consist of the following:
a) Setting up the level: The operation of setting up includes fixing the instrument on the stand and levelling the instrument approximately.
b) Leveling up: Accurate leveling is done with the help of foot screws and with reference to the plate levels. The purpose of leveling is to make the vertical axis truly vertical. It is done by adjusting the screws.
c) Removal of parallax: Parallax is a condition when the image formed by the objective is not in the plane of the cross hairs. Parallax is eliminated by focusing the eye-piece for distinct vision of the cross hairs and by focusing the objective to bring the image of the object in the plane of cross hairs.
Permanent adjustments of Level
To check for the permanent adjustments of level two-peg test method should be performed. Two staffs were placed at A and B of known length (about 50 m). First the instrument was setup on the line near A and both staff readings (Top, Middle, and Bottom) were taken. Then, the instrument was setup at the middle C on the line and again both staff readings on A and B was taken. Then computation was done in order to check whether the adjustment was within the required accuracy or not.