Temporary adjustments of theodolites

Temporary adjustments are a set of operations which are performed on a theodolite to make it ready for taking observations.

These include its initial setting up on a tripod or other stand, centering, levelling up and focusing of eyepiece.

During this, first the screw-clamping ring of the sliding head is loosened and the upper plate of the shifting head is slid over the lower one until the plumb bob is exactly over the station mark.

Leveling of an instrument is done to make its vertical axis adjusted with respect to the apparent force of gravity at the station.

For two spirit vials at right angles: The same principle applies for a bulls-eye level: To obtain an accurate clear sighting, the cross hairs should be in focus; adjust the eyepiece to do this.