Measurement uncertainty in network RTK GNSS-based positioning of a terrestrial laser scanner

This paper reports on investigation of measurement uncertainty in positioning of a terrestrial laser scanner with network RTK (Real-Time Kinematic) service provided by SWEPOS (R), Swedish national network of permanent reference stations for GNSS (Global Navigation Satellite System). To simulate measurements by a scanner, a rotating flat bar fixed to a prism base, attached to a tribrach, was used. The tests have been carried out with both a rotating GNSS antenna (placed at different distances from the centre of rotation - radii) and a stationary antenna, under different time intervals (1-5 min). The results show that it is possible to achieve a standard uncertainty of less than 10 mm in plane and 16 mm in height, independently of the observation time and radius. Hence, network RTK can be used with advantage for precise direct georeferencing of point clouds, not only for determination of the position of the scanner, but also its orientation.