## 4 Results and Discussion
### Performance of Real-Time BDS-3/BDS-2 PPP
As to the accuracy difference between post-processed and real-time solutions in static mode, it is also notable for the BDS-3/BDS-2 PPP (on average 0.9 cm over the three directions), but at a smaller level for the GPS PPP (on average 0.4 cm over the three directions). Figure 14: Distribution of positioning accuracies from different static precise point positioning (PPP) solutions. Figure 16 shows the kinematic positioning accuracies using different precise products, and Figure 17 compares the corresponding time for convergence. As the kinematic position errors may still fluctuate at a level of several centimeters even after a long processing time, for each 24-h session, the RMS statistics of the positioning errors over the last two hours are computed to indicate the kinematic positioning accuracies. For real-time kinematic PPP with BDS-3/BDS-2 observations, there are 87.1%, 94.7% and 59.8% of solutions with position accuracies better than 9 cm in the east, north and up directions, respectively, whereas the corresponding position filters with convergence times shorter than 60 min account for 64.3%, 80.0% and 59.6% in the three directions, respectively. The mean position accuracies of BDS-3/BDS-2 real-time kinematic PPP are 6.7/5.1 cm in east/north directions, and 10.4 cm for the vertical direction, which are worse than the GPS-derived results with statistics of 2.9/2.6 cm and 5.1 cm respectively. A mean convergence time of 66.9/42.9/69.1 min can be achieved for the BDS-3/BDS-2 real-time kinematic PPP in the east/north/up directions, respectively, which is almost thrice that of GPS results. For the post-processing positioning, the use of BDS-3/BDS-2 final precise products leads to cm-level improvement of mean position accuracies (on average 2.6 cm over the three directions) and about 20-min reduction of convergence time (on average 21.9 min over the three directions) compared to the real-time solutions. Improvements between GPS post-processing solutions and real-time solutions are mm-level in position accuracies and several seconds in convergence time, indicating that the accuracies of GPS precise products in the real-time situation are close to those of GPS final precise products. Compared with the BDS-3/BDS-2 post-processed solutions, the improvements of GPS post-processed solutions in the kinematic mode are 41%/32%/41% and 54%/43%/43% for the position accuracies and convergence time in the east/north/up directions, respectively. Figure 15: Distribution of convergence time from different static PPP solutions. Figure 16: Distribution of positioning accuracies from different kinematic PPP solutions. Figure 17: Distribution of convergence time from different kinematic PPP solutions. The space weather event can deteriorate the PPP precision, such as magnetic storms [39], with an expansion of the auroral oval [40], solar flares [41], and ionospheric scintillations [42]. The condition of geomagnetic activity during the studied period (DOY 140-146 of 2020 in this section) is also analyzed. During the analysis period, the geomagnetic activity is at a weak level, and the varying range is 0.7 to 1.3, and \(-\)7 to \(-\)1 nT for the daily mean value of Kp index and Dst index, respectively. Thus, the accuracy differences among different days are not significant for the BDS-3/BDS-2 real-time PPP. It should be noted that the derived positioning performance of BDS-3/BDS-2 real-time PPP in this study could degrade when the geomagnetic activity becomes strong.