Abstract: A target unit comprises equally spaced and crosswise arranged photoelectric converters responsive to a visible or invisible light pulse beam hitting the unit at an area including a center point for producing output pulses. The converters are disposed on four sides of the cross point, and divided into four adjacent groups, adjacent to the cross point and four remote groups, remote therefrom. The area is capable of covering the adjacent group converters but no more of the remote group ones when the center point coincides with the cross point. Counts of the output pulses for each adjacent group and for the associated remote group are added. The sum for the adjacent and remote group pair is subtracted from the sum for the related pair to drive an indicator for simulating the distance and the azimuth of the center point relative to the cross point.