Estimation of Velocities of Ukrainian GNSS Stations in the IGb08 Reference Frame

The cumulative solution for GPS weeks 935–1933 (December 7, 1997–January 28, 2017) was obtained in the GNSS Data Analysis Centre of the Main Astronomical Observatory of the National Academy of Sciences of Ukraine after adjustment of 6993 daily normal equation files received as a result of the regular processing and the second reprocessing campaign of archival observations. The ADDNEQ2 program of the Bernese GNSS Software ver. 5.2 was used. Before the adjustment, the times series of station coordinates received from the mentioned processing were analyzed to find outliers and determine sets of coordinates and velocities. For foreign EPN stations, the files prepared by the EUREF Permanent GNSS Network were used (EPN_outliers.lst and EPN_discontinuities.snx respectively). For 233 permanent GNSS stations, the 356 sets of coordinates and 256 sets of velocities that correspond them were established. According to the duration of observations, the coordinate sets were divided into three groups: (1) less than 1 year (94 sets), (2) 1–3 years (92 sets), (3) more than 3 years (166 sets). Four coordinate sets were excluded from further analysis. The IGb08 reference frame was realized by applying No-Net-Translation conditions on the coordinates of the IGS Reference Frame stations. The velocities of these stations were heavily constrained (10–9 m/year for each components) that, in term of adjustment means, a fixing of velocities values. As result, the coordinates and velocities of the Ukrainian and the Eastern European stations in the IGb08 reference frame at epoch 2005.0 were estimated with high precision. The mean repeatabilities for components of station coordinates are 1.69, 1.40, and 3.63 mm for the north, east, and height components respectively.