*7.1. Evaluation Environment*

The evaluation environment contains a network of control points (6 pillars, 16 ground points, 15 building points) that covers an area of about 1.5 km<sup>2</sup> with variable GNSS conditions (Figure 13). The control point coordinates were determined in a network adjustment using measurements from total stations, GNSS baselines, and levelings. The network is linked to the official German coordinate systems, i.e., ETRS89/UTM32 (European Terrestrial Reference System 1989, Universal Transverse Mercator, Zone 32) for position, and DHHN16 (Deutsches Haupthöhennetz 2016) for physical heights. In addition, the ellipsoidal heights w.r.t. GRS80 (Geodetic Reference System 1980) were determined. The connection between the ellipsoidal heights and the physical heights was realized by using the German Combined Quasi Geoid Model (GCG16) [83]. The network was surveyed in June 2017 and July 2018 for checking its stability [84]. The final control point coordinates are based on a combined network adjustment of both epochs and have estimated standard deviations of <1 mm.

**Figure 13.** Network of control points with six pillars, 15 building points, and 16 ground points. The control points can be signalized with BOTA8 (Bonn Target 8) laser scanning targets (Source: Google Earth, modified).

In addition to the control points, TLS reference point clouds of all buildings in the area of the control points were measured (Figure 14). The TLS scans were captured from multiple stations in two faces and georeferenced using the network of control points like it was done for the calibration field in Section 6.1. The mean absolute error after georeferencing was 1.2 mm. The TLS reference point clouds can be used for an area-based evaluation of mobile laser scanning systems. In addition, a point-based evaluation is possible based on the control points. For this purpose, the pillars and building points can be signalized with special BOTA8 laser scanning targets [82] (cf. Figure 15), which are applicable to both TLS registration and evaluation of mobile laser scanning systems.

**Figure 14.** TLS (Terrestrial Laser Scanning) reference point clouds georeferenced using the control points and BOTA8 (Bonn Target 8) laser scanning targets.
