SURVEYING INSTRUMENT

The present disclosure provides a surveying instrument. The surveying instrument comprises a center unit comprising an optical device and a front lens. The optical device is arranged to emit and/or receive light through the front lens along an optical axis (OA) of the center unit. The surveying instrument further comprises an alidade on which the center unit is rotatably arranged about a first axis (A). The alidade comprises a tilt sensor arranged along a second axis (A). The second axis is orthogonal to the first axis. The alidade further comprises an optical arrangement arranged to form an optical path from a first side of the alidade to an aperture arranged along the second axis at a second side of the alidade. The optical path bypasses the tilt sensor. The center unit is rotatable about the first axis to a predetermined rotational position (P), in which the optical axis aligns with the optical path such that the optical device is arranged to emit and/or receive light through the aperture along the second axis.