## 3 Experimental Evaluation
### Experimental Process  
In this study, the abnormal value of a single sample has been excluded, which refers to a single sample with a small number of satellites participating in the PPP calculation. The excluded samples for static PPP and kinematic PPP are shown in Table 2, where G, C12, and C13, respectively, represent the positioning modes of GPS(L1L2), BDS (B1 cB2a), and BDS (B1 IB3I). The number (DOY) + station name represents the day of year and the station. For example, 337 PIE1 represents the sample of PIE1 on the 337 th day in 2020, and \"all\" represents all days from 336-355.  
For the same observation data, regardless of whether static PPP or kinematic PPP, the number of satellites involved in positioning is the same. This article counts the average number of satellites participating in BDS (B1 CB2a), BDS (B1 IB31), and GPS (L1L2) PPP for 17 stations, as shown in Figure 2. The PPP availability of this station can be better reflected by the average number of satellites. The stations with a small average number of satellites shown in Figure 2 can basically correspond to the stations excluded in Table 2.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{2}{c}{**Static PPP**} & \multicolumn{3}{c}{**Kinematic PPP**} \\ \hline
**C12** & **C13** & **C12** & **C13** & **G** \\ \hline \multirow{8}{*}{337 PIE1} & & & allPIE1 & 336 ULAB \\  & 337 PIE1 & & & 338 LPGS & 341 WUHZ \\  & 340 PIE1 & allPIE1 & & 342 ULAB \\  & 341 PIE1 & 337 LPGS & & 340 CHPG & 342 URUM \\  & 343 PIE1 & 340 LMMF & & 344 URUM \\  & 341 PIE1 & & 341 UNB3 & 345 ULAB \\  & 352 PIE1 & 341 UNB3 & & 345 WUHZ \\  & 353 PIE1 & & 344 CHPG & 346 WUHZ \\  & 353 PIE1 & & & 347 URUM \\  & & & 347 CHPG & 349 WUHZ \\  & & & 351 WUHZ \\  & & & 355 GODN & 355 URUM \\ \hline \hline \end{tabular}
\end{table}
Table 2: Statistics of excluded sample values.  
\begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{2}{c}{**Parameters**} & **Models** \\ \hline \multirow{8}{*}{**Error correction**} & Satellite orbit & GBM precise orbit \\ \cline{2-3}  & Satellite clock & GBM precise clock \\ \cline{2-3}  & Phase wind-up & Model corrected [46] \\ \cline{2-3}  & Phase center offset & igs14.atx \\ \cline{2-3}  & Earth deformation & IERS conventions \\ \cline{2-3}  & Ionospheric correction & Ionosphere-free combination \\ \cline{2-3}  & Tropospheric correction & GPT2\_5W + SAAS + VMF1 \\ \hline \multirow{8}{*}{**Parameter estimation**} & Ambiguity & Piecewise constant, float solution \\ \cline{2-3}  & Troposphere & Random walk \\ \cline{2-3}  & & \(\sigma_{trop}=2\) cm/\(\sqrt{\text{hour}}\) \\ \cline{2-3}  & Station coordinates & Static: constant, \\ \cline{1-1} \cline{2-3}  & Kinematic: random walk (Set to 100 m) \\ \cline{1-1} \cline{2-3}  & Clock correction & White noise \\ \hline \hline \end{tabular}
\end{table}
Table 1: _Cont._For the overall performance of static PPP, due to the limited number of satellites, there are large errors, which have a great impact on positioning statistics and lack statistical objectivity. Figure 3 shows the static PPP error at station PIE1 for BDS-2+3 (B1 IB3I), and the number of satellites involved in positioning on DOY 343 in 2020. In Figure 3, there are less than five satellites participating in static PPP for a long time, and the position information cannot be calculated in static PPP.  
For kinematic PPP, the number of satellites has a very large impact on positioning. When the number of satellites is less than five, abnormal jumps occur, as shown in Figure 4.  
Therefore, in the subsequent data analysis, the above cases are excluded.  
Figure 3: BDS (B1 IB3I) static PPP positioning error and number of satellite (DOY343, 2020).  
Figure 2: Average number of satellites participating in PPP at 17 stations.