A priori vs. In-situ Terrestrial Laser Scanner Calibration in the Context of the Instability of Calibration Parameters

Commonly, terrestrial laser scanners (TLSs) are calibrated on calibration fields so the scanner’s instrumental errors are estimated a priori to a given task. Such approaches presume the stability of errors with time and external influences so that the calibration parameters are valid at future measurements. Alternatively, TLSs are calibrated in-situ during the measurement. Then, there is no need to assume the stability of the calibration parameters. However, these in-situ strategies only work out under specific conditions. Thus, it is important to know the calibration parameters’ stability to optimally select or combine the calibration approaches. Herein, we investigate the parameter stability and possible causes for their changes. Our results indicate that the changes can be tracked and partially modeled based on the internal warming-up of the instrument, the ambient temperature, and the compensator bias. We reduced the parameter variability by modeling these effects and quantified the magnitudes of the parameter changes.