# Assessment of GNSS Galileo Contribution to the Modernization of CROPOS's Services
## 3 Results
### Static Observations and Processing in Trimble Business Center
Each static session was processed twice: once using all available satellite system observations (GPS + GLO + GAL + BDS) and the second time using GAL-only data. Four different project types were created according to the schema outlined in Figure 4: GGGB project providing nine solutions (each session provided one solution), 'GAL-only' project providing nine solutions (each session provided one solution), 'GGGB (daily solution)' project providing one solution, and 'GAL-only (daily solution)' providing one solution. The network adjustment was performed in each project according to the procedure outlined in Trimble Geospatial [67]. It was carried out in two steps: minimally constrained network adjustment followed by the constrained network adjustment. In order to obtain two individual daily solutions, all sessions were combined, leading to a single solution based on GGGB observations and one solution based on GAL-only observations. Since the daily solution based on all available data (GGGB) was considered the most reliable one, it was considered as a REFERENCE solution for further analysis of the solutions obtained by kinematic VPPS observations. A single daily solution based on 'GAL-only' observations was compared with the REFERENCE solution. The differences \(\Delta\)E = 0.0004 m, \(\Delta\)N = \(-\)0.0001 m, and \(\Delta\)H = \(-\)0.0010 m (displayed in Figure 5) have provided almost perfect matching between the two results. Figure 4: Static post-processing schema in TBC: each session was processed providing solutions based on GGGB and GAL-only observation data. If each individual session result based on GAL-only data is compared to the REFERENCE, the following maximum absolute difference values are obtained: MAX (ABS (\(\Delta\)E)) = 0.0046 m, MAX (ABS (\(\Delta\)N)) = 0.0046 m, and MAX (ABS (\(\Delta\)H)) = 0.0163 m. The differences between each individual 'GAL-only' static session and the REFERENCE are shown in Figure 6.  
The values show a variable sign, confirming that the differences generally show stochastic (random behavior). Session A-6 presents an exception where the difference reached its maximum \(\Delta\)H = 0.0163 m. When the 2D differences (planar differences between each solution and the REFERENCE) are examined, it turns out that the maximum value reached \(\Delta\)d = 0.0053 m, whereas the 3D (spatial) differences reached their maximum  
Figure 5: Coordinate differences (delta E, delta N, delta H) of static ‘GAL-only’ (daily solution)-REFERENCE. Figure 6: Coordinate differences (delta E, delta N, delta H) between individual static ‘GAL-only’ sessions and the REFERENCE. to \(\Delta\)D = 0.0170 m. When the results of the A-6 session are excluded, the maximum value is \(\Delta\)D = 0.0063 m. Overall, it can be stated that individual GAL-only sessions have enabled a reliable solution compared to the REFERENCE position obtained by all systems' observation data. The random sign of coordinate differences across all sessions can be regarded as confirmation of the absence of significant biases. The analysis of observation data present in the RINEX observations files across all sessions led to the conclusion that the numbers of observed satellites were in the following intervals: GPS (7-10), GLO (5-7), GAL (5-8), and BDS (11-17), with all observed satellites being in the interval of 30-41. In the same manner, all individual sessions processed with all available observation data systems (GGGB) have shown slightly better results, with the maximum absolute value of coordinate differences given as follows: MAX (ABS (\(\Delta\)E)) = 0.0030 m, MAX (ABS (\(\Delta\)N)) = 0.0035 m, and MAX (ABS (\(\Delta\)H)) = 0.0031 m leading to the MAX (\(\Delta\)d) = 4.4 mm and MAX (\(\Delta\)D) = 4.6 mm. As expected, those results are better in comparison to results obtained with GAL-only individual sessions data. As in the previous analysis, all coordinate difference values show random (stochastic) behavior confirming the absence of significant biases.