Abstract: An improved photoelectric displacement detector is disclosed which includes (a) a light receiving part (1) having a pair of solar battery panels (1b, 1c) vertically arranged adjacent to each other, (b) a vertical motion mechanism (2) which is driven by a motor (3) to vertically linear-shift the light receiving part (1), (c) a vertical light quantity difference detection part (4) for detecting, based on signals from the solar battery panels (1b, 1c), a difference between the quantity of light received in the solar battery panel (1b) and the quantity of light received in the solar battery panel (1c) and (d) a CPU (5) for controlling the operation of the motor (3) according to the received light quantity difference detected by the vertical light quantity difference detection part (4). Reference laser light is sent onto the light receiving part (1) and the light receiving part (1) is vertically shifted in order that the aforesaid received light quantity difference is cancelled to zero.

Abstract: A reflector provided on a land is automatically collimated in such a way that it always comes to the center of the field of view of an automatic tracking type measuring apparatus provided on a platform. When the platform moves vertically or horizontally in this state, the reflector moves within the field of view. Then, a drive signal is supplied to a servo system to cause the reflector to come to the center of the field of view. Based on data measured by the apparatus, the platform is positioned.