## 6 Effects of Multipath on GNSS Carrier Post-Fit Residuals
### Single Point Positioning  
The two stations (KBG1 and KBG2) are continuously operating with all four constellations recorded at 1 s and 30 s epochs. Typically, positioning from pseudorange measurements with broadcast ephemeris is possible when at least four satellites are visible in the sky. At our latitude, at least seven satellites are observed from any of the constellations. Single-point positioning (SPP) can readily be available using only psuedorange measurements at every epoch or once every 24 h. In GNSS processing, the carrier phase ambiguity resolution is generally initialized using pseudorange measurements; multipath-corrupted observations can consequently take longer to resolve the ambiguities to integers [13]. Figures 11 and 12 present the single-point positioning evaluated for multi-GNSS constellations with and without Eccosorb materials as explained in Section 2. The site-specific multipath shows an effect on the position qualities from pseudorange observations looking at the uncertainty derived in north-south (NS) and east-west (EW) directions for all four GNSS constellations employed here. For station KBG1 with Eccosorb, the standard error for GPS in the NS direction is 1.7 m, while in the EW direction, it is 1.3 m; for Galileo, it is 0.7 m and 0.5 m respectively, highlighting the much better accuracy achieved by Galileo. For GLONASS, the NS and EW standard errors are 5.9 m and 4.0 m, respectively, with the lowest accuracy coming from BeiDou at 7.4 m and 7.7 m, respectively. We also evaluated the instantaneous accuracy of SPP for the close-by station, KBG2 without Eccosorb. The standard error in the NS direction for GPS is 2.0 m and 1.7 m in the EW direction; for Galileo, it is 0.9 m and 0.9 m; for GLONASS, the NS and EW standard errors are 7.6 m and 4.0 m; and the lowest accuracy comes from BeiDou, with 7.1 m and 8.0 m, respectively. The reductions in standard errors are significant for all the multi-GNSS-based SPP solutions for the station with microwave-absorbing material. For GPS, the improvement is between 15 and 23%; for Galileo, it is between 22% and 45%; GLONASS is 22%; and BeiDou is about 4%. In addition, for the station KBG1, we computed a combined GPS + GLONASS + Galileo + BeiDou solution with an NS direction accuracy of 1.7 m and an EW direction accuracy of 1.4 m. Similarly, for the KBG2 station, the combined GPS + GLONASS + Galileo + BeiDou solution shows an accuracy of 2.0 m and 1.6 m in the NS and EW directions, respectively. The Eccosorb material improves the single-point positioning solution accuracy by 12 to 15% for the combined solution.  
The microwave-absorbing material Eccosorb AN-W-79 shows convincing results in reducing the noise level of the code measurements.  
Figure 10: The RMS values of the post-fit carrier phase residuals (LC) of the L1 and L2 phase observables for station BKG1 with the microwave absorber in blue solid colour and for station BKG2 in dark green solid colour for elevation angles with a bin width of 1\({}^{\circ}\).  
Figure 11: Single-point positioning for site KBG1 with Eccosorb absorbing material surrounding its antenna using multi-GNSS observables. Results are shown in blue for GPS (**a**), in red for Galileo (**b**), in dark green for GLONASS (**c**) and cyan for BeiDou (**d**), and in the magenta for COMBINED (**e**). The positioning accuracy using GPS in the north-south direction is 1.7 m, and in the east-west direction, it is 1.3 m; for Galileo, it is 0.7 m and 0.5 m, respectively, highlighting the added value of Galileo; for GLONASS, it is 5.9 m and 4.0 m; and the lowest accuracy comes from BeiDou, with 7.4 m and 7.7 m. We have also derived a combined GPS + GLONASS + Galileo + BeiDou solution with a north-south direction accuracy of 1.7 m and east-west accuracy of 1.4 m.