A large scale 3D positioning method based on a network of rotating laser automatic theodolites

This paper presents a new 3D positioning method of setting up a network of rotating laser automatic theodolites (RLAT) for the large scale metrology. In this system, each RLAT consists of two laser fans rotating about its own Z axis at constant speed and an optical sensor is used to detect the pulse signals of sweeping laser fans. Instead of estimating indirectly the two space angle of laser fans, the rotating laser fan is modelled as a time varying parametrical vector, which establish a new relationship between rotating angle of laser fan and time when laser fan sweeps over 3D point. Based on that, the network of RLATS is mathematically modelled as a non-linear equation system and a union calibration method is proposed to estimate the parametrical vectors of each RLAT and all transformation among network of RLATS by solving non-linear objective function optimally. A prototype network of RLATS is developed and experiment results show the validity of positioning 3D location in a large scale.