US Patent 7110102 Working position measuring system

A working position measuring system, comprising a rotary laser device for irradiating and rotating a laser beam and a photodetection sensor device for receiving the laser beam and for detecting a working position, wherein the rotary laser device comprises a laser projector for projecting at least two fan-shaped beams with at least one beam tilted, and the photodetection sensor device comprises at least one photodetection unit for receiving the fan-shaped beams and an arithmetic unit for calculating an elevation angle relative to the rotary laser device based on photodetection signals produced when the photodetection unit receives the light beam.