Transferability of an estimation procedure for distance deviations of terrestrial laser scanners from laboratory to on-site conditions

Employing terrestrial laser scanners (TLS) for geodetic deformation measurements requires attaining the highest possible accuracy. In this paper, we estimate the influence of varying incidence angles (IA) and materials on measurements regarding the distance component. Considering not only stochastic characteristics, the use of a scanning total station enables additionally the study of systematic distance deviations. By using the total station ocular, the device is brought into the local coordinate system of a laser tracker via position resection and intersection. The point cloud recording, with a Close-Range scanner, represents the reference. Due to transformation into a common coordinate system, defined by a laser tracker, a distance driven point comparison is possible. To test a large number of conditions an automated setup was developed. For each device, a suitable interface was implemented in the Robot Operating System. After the specimen has been set up, an automatic measurement can be performed for data acquisition. We can demonstrate that different building materials and varying IAs cause systematic distance deviations up to 3 mm magnitude. For measurement objects, this kind of correction must be considered, especially when the measurement configuration varies between measurement epochs. It can be demonstrated that the values and characteristics observed in the laboratory agree to those obtained on-site. However, the chosen approach thereby reveals previously unrecognized challenges that need to be considered for the use of TLS in high-accuracy deformation analysis.