Abstract: This laser beam detector system may comprise an array of photodetectors usable in conjunction with a laser employed to define an elevation or grade. The detector array is utilized on an elongate device having a plurality of faces, with a plurality of detectors disposed in a consistently spaced arrangement on each of the faces. The detectors of each face have a field of view different from the field of view of the detectors of the other faces, and each detector on each face of the array is disposed at the same height as a corresponding detector on each of the other faces. Importantly, each group of detectors at the same height are electrically interconnected into a co-functioning group. Our novel arrangement is such that a laser beam incident on any detector of a co-functioning group is detected, with the position of the detector upon which the beam impinged being identified, and a readout indicative of that detector then provided.