# Assessment of BeiDou-3 and Multi-GNSS Precise Point Positioning Performance
## 5 Data Tests and Results Analysis
### Positioning Accuracy and Convergence Time  
#### 5.1.1 Static Results and Analysis  
In order to compare the difference of the positioning performance between GPS-only, BDS-2-only, BDS-2/BDS-3, GLONASS-only, Galileo-only, GPS/BDS-2/BDS-3, GPS/GLONASS, GPS/G Galileo, BDS-2/BDS-3/GLONASS, BDS-2/BDS-3/G Galileo, GLONASS/G Galileo, and GPS/BDS-2/BDS-3/GLONASS/G Galileo, the static PPP processing results for 12 different processing cases are presented and analyzed in this section. Figures 3 and 4 depict the static PPP positioning errors, the number of visual satellite, and PDOP at BRCH for GPS-only, BDS-2-only, BDS-2/BDS-3, GLONASS-only, Galileo-only, and GPS/BDS-2/BDS-3/GLONASS/G Galileo, respectively. It is obvious that the problems of the insufficient amount of BDS-2 visual satellite and the poor satellite constellation structure at BRCH are solved with the opening of the global navigation service of BDS-3, and there are no obvious gap between the BDS and other navigation system. When compared with the number of visual satellite and PDOP of single system and multi-GNSS, the measurement fusion technique of multi-GNSS can increase the number of visual satellites and reduce the PDOP value. From the prospect of positioning, no matter GPS, BDS-2, BDS-2/BDS-3, GLONASS, and Galileo, they all have achieved a centimeter-level or even a millimeter-level convergence effect, and multi-GNSS increases the positioning accuracy and the stability of positioning and it decreases the convergence time over the single-constellation and dual-constellation PPP. Figure 3: Static PPP positioning errors at BRCH for 12 different processing cases on DOY 024 in 2019. Figure 5 depicts the root mean squares (RMS) statistics of 16 stations for 30 days in the north (N), east (E), and up (U) coordinate components, as well as RMS for the three-dimension (3-D) position, in order to scientifically and accurately evaluate the positioning accuracy of each navigation system and its contribution to multi-GNSS. The RMS statistical values using the positioning errors in the last one hour in which the position solutions in all three components have reached stable values. We can draw the following viewpoints based on the solutions of the selected observation data. It is noticed that the BDS-2-only positioning accuracy is comparable to GPS-only and GLONASS-only with a difference. However, there is no obvious disparity between BDS and GPS, GLONASS with the opening of BDS-3. It is worth mentioning that the static BDS-2/BDS-3 PPP improves the position accuracy by 17.05%, 24.42%, and 35.65% over the BDS-2-only PPP in three coordinate components, respectively. The RMS of global position errors for static BDS-2/BDS-3 PPP and Galileo-only PPP are 10.7, 19.5, 20.4 mm, and 6.9, 18.6, 19.6 mm, respectively, as the same level as GPS and GLONASS. However, there is a slight difference of positioning accuracy between BDS, Galileo, and GPS. The PCO and PCV receiver corrections of BDS and Galileo are corrected by using the correction value that was provided by GPS, which could cause the positioning accuracy of BDS and Galileo to be slightly worse than that of GPS. The precise orbit determination strategy of BDS-3 has not yet matured in terms of in-orbit estimations of the phase center correction for the BDS-3 satellites, precise attitude model, and the solar radiation pressure model [30], which is why the positioning accuracy of BDS is slightly worse than that of GPS. Now, turn to the multi-GNSS PPP, the contributions of BDS-2/BDS-3 and Galileo to the improvement of multi-GNSS positioning accuracy. The GPS/BDS-2/BDS-3, GPS/Galileo, BDS-2/BDS-3/GLONASS, BDS-2/BDS-3/Galileo, and GLONASS/Galileo PPP achieves better positioning accuracy than single-constellation PPP. It is worth mentioning that the GPS/BDS-2/BDS-3/GLONASS/Galileo PPP positioning accuracy improvement of 4.75% over the GPS case, 31.45% over BDS-2/BDS-3 case, 32.17% over GLONASS, and 25.81% over Galileo in the three-dimensional (3-D) components is achieved.