Geometric accuracy investigations of terrestrial laser scanner systems in the laboratory and in the field

This paper summarizes recent research into current terrestrial laser scanners undertaken by the HafenCity University Hamburg and gives an assessment of the geodetic accuracy of the latest generation of scanners. Three separate independent test methods are presented to investigate the geometric accuracy of terrestrial laser scanners under laboratory conditions: (a) distance measurement accuracy to b/w targets and spheres on the 20-m comparator track, (b) comparison of spatial distances in the 3D test field on b/w targets, and (c) investigation of the flatness deviation following the guideline VDI/VDE 2634 (VDI/VDE 2012) on a flat stone slab. The following laser scanners were tested in the lab: Leica BLK360 (2017), Leica RTC360 (2019), Z+F IMAGER 5016 (2019, 2020), Z+F IMAGER 5010 (2020), and Faro Focus(3D) X330 (2020). The reference measurements were realised with the Leica Absolute Tracker AT960 (2017, 2020) and with the Leica TS60 total station (2019). The results of the geometric accuracy tests in the laboratory show very small deviations in the range of 1-2 mm for most of the scanners, thus corresponding to the manufacturer's specifications. In addition, five laser scanners were tested in accordance with instruction sheet 7-2014 of the German Society for Geodesy, Geoinformation and Land Management (DVW) for standardised testing of terrestrial laser scanners in the outdoor area of HafenCity University Hamburg. For the execution of the field test procedure, only the standard equipment and software of the respective manufacturers were used. The entire field test procedure, including data acquisition and evaluation, was completed within 4 to 5 h for each scanner. As expected, no significant distance or angle deviations were detected in any of the measurement systems, so that the tested laser scanners are ready-to-use, taking into account the measurement volume recorded.