SURVEYING INSTRUMENT AND METHOD OF CALIBRATING A SURVEY INSTRUMENT

A surveying instrument comprises a base; an alidade rotatable about a first axis relative to the base; and an optical measuring instrument having a measuring axis rotatable about a second axis relative to the alidade. A beam path can be provided for a light beam using components including a light source, lenses, mirrors, beam splitters, and a position-sensitive detector. The surveying can be calibrated by performing plural measurements at different orientations of the alidade relative to the base and different orientations of the measuring instrument relative to the alidade using the above components.