Impact of Baseline Distance and Interstation Height Difference On the Accuracy of GPS-Derived Station Coordinates

Abstract

This paper investigates the accuracy comparison of scientific and commercial GPS processing software for varying length of baselines and interstation height differences. European Reference (EUREF) Permanent Network Stations were used for the processing. GAMIT/GLOBK research GPS processing software (version 10.6) and Leica Geo Office (version 8.4) commercial GPS processing software were chosen for the experiment. TUBO EUREF GPS station was taken as a known station whose three-dimensional (3D) published coordinates are precisely known and the other stations were taken as unknown points whose 3D coordinates are calculated after the processing. In this way, minimally constrained adjustment was performed for each unknown station within the EUREF network and their coordinates were calculated w.r.t. TUBO station with using each software. Only independent (non-trivial) baselines are processed between known station and unknown stations. Processing was conducted for 10 different days with 24 hours rinex data of the stations. When choosing the GPS stations, we consider the interstation height difference and baseline distance between the chosen GPS stations. Baseline distances varying from 131 km to 495 km. Interstation height differences varying from 4 m to 1620 m. After the processing, differences between the calculated 3D Cartesian coordinates of the stations whose coordinates were assumed unknown and the published true coordinates of these stations were transformed to topocentric coordinates (north, east, up) to observe the error component in 3D space. Results show that vertical accuracy obtained from commercial software is significantly low and not consistent comparing with the scientific software. There is no significant difference observed for horizontal accuracy between the software but the horizontal accuracy obtained from the scientific software is slightly better than the commercial one. There is no strong correlation found between the baseline distance and the accuracy for each software but this is not the issue for interstation height differences. Regarding the interstation height differences, it is observed that height difference between station pairs effect the accuracy in up component. As height difference between baseline points grow vertical, error becomes larger, especially for commercial software.