Empirical assessment of obstruction adaptive elevation masks to mitigate site-dependent effects

Site-dependent effects are accuracy-limiting factors in static and kinematic GNSS-based positioning applications since they cannot be minimized using differential techniques. In general, these effects are separated into signal diffraction, non-line-of-sight (NLOS) signal reception, multipath, and quality of the satellite geometry. In particular, signal diffraction and NLOS reception can lead to huge positioning errors. We present a straight forward approach to mitigate signal diffraction and NLOS reception by forming obstruction adaptive elevation masks, based on terrestrial laser scans. This enables an improvement of the positioning accuracy in high-precision static GNSS applications, even under challenging GNSS measurement conditions. By means of empirical investigations, the approach was tested successfully, and the site-dependent systematic errors can be separated and analyzed. Furthermore, the site-dependent effects and their error sources are assessed in relation to their impact on the accuracy of the positioning solution. We demonstrate that despite poor GNSS measurement conditions, positional accuracies better than 2 mm can be achieved and the ambiguity fixing rate is improved significantly.