HOW ARE THE THEODOLITE LEVEL

There are two types of adjustment in the theodolite
Permanent adjustment

The temporary adjustment has to be made for every setup of the instrument.  The temporary
adjustment of theodolite has three steps, setting up over or under station point, leveling and
elimination of parallax. In the setting up theodolite centered and approximate leveling is done
by plumb bob and tripod legs. For the exact level of theodolite means the vertical axis of the
theodolite should truly be vertical when theodolite is leveled.It is done by leveling screws of
plate level.


There are two types of theodolite plate level, one has three leveling screws and other has
four leveling screws.

Leveling procedure for if the three leveling screws.

    Set the instrument on the tripod and complete the centering and approximate leveling process by the help of tripod legs. Tight the upper vernier clamp and loosen the lower vernier clamp screw. Turn the instrument about either of its axes until the longer plate level is parallel to any pair of leveling screws. The other plate level will then be parallel to the line joining the third screw and the midpoint of the line joining the first pair. Bring the bubble to the center of its run by both screws. The thumbs move either towards each other or away from each other. Bring the other bubble to the center of its run by turning the third leveling screw. Repeat the process until finally, both bubbles are exactly center. For greater accuracy, you can use a reference to the altitude level. Now rotate the instrument about its vertical axes, if the bubbles remain constant of its position then the plate levels are in correct adjustment.
    four leveling screw.

    Leveling procedure for if the four leveling screws.

    If the instrument has four leveling screws, for the level tube at near the 2 no. level screw. Turn level screws 3 and 4 inward or outward.  screw. Turn level screws 3 and 4 inward or outward. For the level tube near the  3no. level tube. turn the level screws 1 and 2.

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