SURVEY INSTRUMENT

The present invention provides a survey instrument, which comprises a solid state image sensor 4 where an image from a telescope is formed, an emitter 6 for emitting flash light toward a target, and a survey controller for detecting position of the center of the target on the solid state image sensor based on difference of image signals between on condition and off condition of the emitter of the solid state image sensor, or it comprises a telescope rotatable around at least one of vertical shaft center and horizontal shaft center, an angle detector for detecting angle of the telescope, a memory for memorizing image signal from the solid state image sensor, and a survey controller for calculating angular displacement based on angles which are detected by the angle detector when image signals in on and off conditions of the emitter are incorporated, for calculating difference between the two image signals by shifting them so that angular displacement of each image signal are offset, and for detecting position of the center of the target from the difference of the two image signals.