Investigating the resolution capability of terrestrial laser scanners and its impact on the effective number of measurements

The resolution capability of terrestrial laser scanners does not necessarily equal the scanning resolution. Laser scanners can acquire the surrounding with a point distance of less than a millimeter on ten meters but the footprint size amounts to at least a few millimeters. Hence, neighboring laser spots overlap and they are correlated as they do not provide individual information about the object. This study provides a new methodology to determine the spatial expansion of the resolution capability of terrestrial laser scanners in the angular direction for distances up to 80 m. It is demonstrated that the Leica ScanStation P20 better resolves objects in the horizontal direction than in the vertical direction. Furthermore, the correlation of neighbored range measurements is empirically derived from the resolution capability and the effective number of measurements is determined. This provides a more realistic measure of the number of uncorrelated points in a scan. It is demonstrated that the resolution capability has a big impact on the correlation of the scan points as the number of uncorrelated points is reduced by up to 93% depending on the scanner settings.