## 4 Results and Discussion
### Performance of Real-Time BDS-3/BDS-2 PPP  
The datasets from 147 stations spanning a week are adopted to evaluate the real-time BDS-3/BDS-2 PPP performance in both kinematic and static scenarios. The BDS-3/BDS-2 post-processed PPP solutions as well as the solutions using GPS observations in both post-processing and real-time modes are also generated for comparison. The final precise satellite products from IGS and WHU are used for GPS PPP and BDS-3/BDS-2 PPP in post-processing mode, respectively. The PPP processing is conducted day-by-day, and the daily position solutions are used for analysis in this section. It should be noted that PPP usually features high position errors at the beginning of the day, and then the position errors gradually decrease. Actually, the change process of position errors from a high level to an acceptable level is not corrected here, and the convergence time is usually taken as an index to describe this. As to the statistic of position accuracies, only the fully converged position solutions after a long processing time are employed. Figures 14 and 15 show the distribution of positioning accuracies and convergence time from different static PPP solutions, respectively. The percentage of position solutions with positioning accuracies worse than 6 cm is indicated by the bar near the 6 cm in Figure 14, and it is a similar case for the position solutions with convergence time longer than 90 min in Figure 15. The absolute value of the position error at the last epoch for each 24-h session is taken as the fully converged positioning accuracy of this data set in the static mode. The convergence of positioning at a specific epoch is identified when the position errors are lower than 0.1 m for the next 10 epochs. We take the  
Figure 13: Statistics of errors of GPS real-time precise satellite orbits and clocks. time spans from the first epoch to the converged epoch as the convergence times. The BDS-3/BDS-2 real-time PPP solutions with static position accuracies better than 2 cm account for 77.7%, 92.0% and 60.6% in the east, north and up directions, respectively, whereas the derived statistics are 62.9%, 77.6% and 58.7% in the three directions for the corresponding position filters with convergence times shorter than 30 min, respectively. The statistics about the convergence time are derived from an accumulation of the percentages for the bars with a convergence time lower than 30 min in Figure 15. The average results over all the employed days and stations are also computed, and they are presented in each panel. We can see that, although the mean east/north/up positioning accuracies using GPS real-time products are higher (i.e., 0.6/0.8/1.5 cm) and the convergence times are also obviously shorter (i.e., 13.4/7.1/15.9 min), the static positioning using BDS-3/BDS-2 real-time products can also converge to the centimeter level within about 30 min, with mean east/north/up position accuracies of 1.8/1.2/2.5 cm and convergence time of 32.9/23.7/32.8 min. The solutions of BDS-3/BDS-2 static positioning have mean east/north/up position accuracies of 0.8/0.4/1.6 cm in the post-processing mode, which are only slightly larger than the values of 0.3/0.2/1.2 cm of GPS post-processed results, but the convergence performance of the BDS-3/BDS-2 one is still significantly worse than the GPS one. The convergence of BDS-3/BDS-2 post-processing solutions consumes dramatically less time than the BDS-3/BDS-2 PPP using real-time products (on average 10.6 min of reduction over the three directions), and the average value is 21.9/12.9/22.7 min. In contrast, those GPS static positioning using real-time products has a similar convergence performance with its post-processing solutions, i.e., 13.0/6.3/14.3 min, which also confirms the high quality of GPS precise satellite products in the real-time situation.