Terrestrial laser scanners datum transformation: insignificant analysis of scale factor

Abstract

Due to the measurement mechanism employed by terrestrial laser scanners (TLSs), the pre-processing procedure has become crucial procedure to orient all acquired data into global or ground coordinate system. Rather than utilising all seven-transformation parameters, most of TLS practitioners have neglected the scale factor. Taking into consideration the uncertainties in deriving range data, disregarding the scale factor in datum transformation computation could jeopardise the quality of pre-processed results. To rigorously examine this argument, two experiments have been designed by considering the element of multi distances and multi sensors. Utilising phase (i.e. Faro Focus 3D) and pulse-based (i.e. Leica ScanStation C10) scanners, both experiments were carried out with computation of seven (7) transformation parameters and scale factors were extracted for the assessment. With the aid of statistical analysis, the computed scale factors were mathematically differentiate to the ideal value (i.e. 1.000 or no scale effect). Under 95% confidence level, the null hypotheses for both experiments have indicate an agreement that scale factor can be neglected in datum transformation process for both types of terrestrial laser scanners.