The Impact of Angle Parameterisation on Terrestrial Laser Scanner Self-calibration

The angular fields of view in which a terrestrial laser scanner captures data differ according to instrument construction. Both the socalled panoramic and hybrid instruments scan through a full horizontal field of view but their vertical fields of view can differ considerably in terms of range and mode of data acquisition. The differences in operational mode govern the allowable range for each of the two angular observables, namely the horizontal direction and the elevation angle, and, ultimately, their parameterisation as observation equations. The impact of the angle parameterisation on the quality of terrestrial laser scanning instrument selfcalibration has been studied. Specifically, the correlation between the scanner orientation angles and the collimation axis error coefficient, whose estimation in terrestrial laser scanner self-calibration has been reported to be unreliable as a result of this mechanism, was examined. It is been demonstrated with both simulated and real data that the angle parameterisation used for hybrid-type scanners is not only the cause of unreliable collimation axis error estimation but is also the reason for the reported ineffectiveness of certain self-calibration network design measures, notably the capture of scans having orthogonal orientations from the same nominal location