## 3 Results
### Performance of Multi-System PPP with Precise Products from Different Analysis Centers
#### 3.4.2 Static Position Solutions
In contrast to the post-processed results, the positioning performance of the single-system cases (except for G-PPP) is still inferior to GREC-PPP even after a long processing time. Table 12 illustrates the real-time PPP statistical results with CNES precise products in the static mode. It should be noted that all the following statistics are only valid for the long-term performance of PPP. Similar to the post-processed PPP results, the positioning accuracy of G-PPP is comparable to that of the multi-system combined cases, but the R-PPP, E-PPP and C-PPP obtain worse positioning accuracy by several millimeters in the east and up directions than the other five combination cases. Similarly, the joint use of multi-system observations can reduce the convergence time. The convergence time improvement is 74%/74%/60% for GR-PPP over R-PPP, 46%/47%/47% for GE-PPP over E-PPP, 61%/68%/52% for GC-PPP, over C-PPP, and 28%/22%/31% for GREC-PPP over G-PPP in the east/north/up directions, respectively. The positioning performance of real-time static PPP is only slightly worse than that of post-processed static PPP for G-PPP, E-PPP and dual-system combined PPP, but it is not the case for R-PPP and C-PPP. The performance degradation is smaller than 6 min on the convergence time, and 0.7 cm on the positioning accuracy for G-PPP, E-PPP and dual-system combined PPP. In comparison with post-processed PPP, the convergence time of real-time PPP is increased by 25.4-28.1, 14.1-15.2 and 14.4-15.6 min, and the \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**System Combination**} & \multicolumn{3}{c}{**Convergence Time (min)**} & \multicolumn{3}{c}{**Positioning Accuracy (cm)**} \\ \cline{2-7}  & **East** & **North** & **Up** & **East** & **North** & **Up** \\ \hline G-PPP & 10.3 & 5.4 & 14.5 & 0.4 & 0.2 & 1.1 \\ R-PPP & 20.2 & 10.2 & 19.4 & 0.6 & 0.3 & 1.4 \\ E-PPP & 11.7 & 6.7 & 17.3 & 0.5 & 0.4 & 1.3 \\ C-PPP & 15.8 & 9.9 & 15.4 & 0.4 & 0.4 & 1.0 \\ GR-PPP & 8.3 & 3.7 & 9.4 & 0.3 & 0.2 & 1.1 \\ GE-PPP & 7.1 & 4.2 & 9.4 & 0.3 & 0.2 & 1.1 \\ GC-PPP & 7.1 & 3.8 & 8.6 & 0.3 & 0.3 & 0.9 \\ GJ-PPP & 10.2 & 5.3 & 13.9 & 0.4 & 0.2 & 1.1 \\ GRECJ-PPP & 5.9 & 2.6 & 6.3 & 0.2 & 0.2 & 1.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Static positioning accuracy and convergence time of post-processed PPP (long-term performance of PPP based on daily observations) with ESA products for different system combinations using the datasets from 29 stations spanning a week. positioning accuracy is reduced by 0.9, 0.5-0.6 and 0.6-0.7 cm for R-PPP in the three directions, respectively. Regarding C-PPP, the corresponding performance degradation in the three directions is 11.0-11.9, 9.5-10.3 and 11.4-12.7 min, and 0.8-1.1, 0.6 and 1.0-1.3 cm in terms of convergence time and positioning accuracy, respectively. The real-time static GREC-PPP can achieve a convergence time of 8.7, 5.2 and 11.2 min and a positioning accuracy of 0.6, 0.8 and 1.3 cm in the east, north and up directions, respectively. The post-processed static GRECJ-PPP shortens the convergence time by 1.8-2.8, 2.1-2.6 and 4.1-4.9 min (21-32%, 40-50% and 37-44%),  
WHU, GFZ and ESA products for different system combinations, respectively. It should be noted that all the following statistics are only valid for the long-term performance of PPP. As to the short-term performance of PPP, the relevant information could be found in the literatures [6; 7; 8]. Different from the static PPP solutions, both the positioning accuracy and convergence time of kinematic PPP solutions can benefit from the multi-system combination.