## 3 Results
### Comparison between BDS Single-System and Joint POD
#### 3.3.1. Overlapping Arcs Precision  
Table 11 and Figure 5 show that in terms of the average RMS of GEO, IGSO, and MEO satellites, the precision of strategy 1 is much better than that of strategy 3. A comparison of the 3D precision of strategies 1 and 3 reveals that the accuracy of GEO satellites improves by 9.5%, whereas the accuracy of the IGSO and MEO satellites improves by 35.5% and 49.1%, respectively. The results show that the BDS/GPS joint orbit determination has the greatest impact on MEO satellites, followed by IGSO satellites, which can be attributed to the global coverage of MEO satellites. In the joint orbit determination, the GPS data are used to determine accurate station coordinates, \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**PRN**} & \multirow{2}{*}{**Normal**} & \multirow{2}{*}{**MEAN**} & \multicolumn{2}{c}{**STD**} & \multicolumn{2}{c}{**RMS**} \\ \cline{3-8}  & & & **S3** & **S4** & **S3** & **S4** & **S3** & **S4** \\ \hline C01 & 69 & \(-65.1\) & \(-64.5\) & 18.3 & 17.7 & 67.6 & 66.9 \\ C08 & 20 & 0.9 & 1.4 & 4.6 & 6.0 & 4.6 & 6.1 \\ C10 & 33 & \(-3.1\) & \(-9.4\) & 13.2 & 13.9 & 13.4 & 16.6 \\ C11 & 65 & \(-0.7\) & 1.0 & 4.7 & 5.5 & 4.8 & 5.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: SLR assessment of strategies 3 and 4 (unit: cm). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Strategy**} & \multicolumn{2}{c}{**Along-Track**} & \multicolumn{2}{c}{**Cross-Track**} & \multicolumn{2}{c}{**Radial**} & \multicolumn{2}{c}{**3D**} \\ \cline{2-9}  & **S3** & **S4** & **S3** & **S4** & **S3** & **S4** & **S3** & **S4** \\ \hline C06 & 10.3 & 12.1 & 20.4 & 44.1 & 6.5 & 7.2 & 24.0 & 23.3 \\ C07 & 10.2 & 13.1 & 18.8 & 22.2 & 9.5 & 12.2 & 23.5 & 29.4 \\ C08 & 12.8 & 10.0 & 19.6 & 24.7 & 6.3 & 7.2 & 24.9 & 27.5 \\ C09 & 11.9 & 17.2 & 21.0 & 22.0 & 5.6 & 7.6 & 25.0 & 29.3 \\ C10 & 14.0 & 27.9 & 18.4 & 24.8 & 7.7 & 8.6 & 24.7 & 39.0 \\ C15 & 15.9 & 14.6 & 15.4 & 19.6 & 5.6 & 5.9 & 23.1 & 25.4 \\
**Mean** & **12.5** & **15.8** & **18.9** & **26.2** & **6.9** & **8.1** & **24.2** & **29.0** \\ \hline C11 & 14.5 & 13.1 & 7.9 & 9.7 & 4.9 & 4.2 & 17.3 & 17.1 \\ C12 & 16.1 & 15.6 & 8.4 & 10.6 & 5.2 & 4.8 & 19.0 & 19.6 \\ C14 & 13.7 & 14.8 & 11.2 & 10.5 & 4.7 & 4.7 & 18.6 & 19.2 \\
**Mean** & **14.8** & **14.5** & **9.1** & **10.3** & **4.9** & **4.6** & **18.3** & **18.6** \\ \hline \hline \end{tabular}
\end{table} 
Table 9: _Cont._ \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**PRN**} & \multirow{2}{*}{**Normal**} & \multirow{2}{*}{**MEAN**} & \multicolumn{2}{c}{**STD**} & \multicolumn{2}{c}{**RMS**} \\ \cline{3-8}  & & & **S3** & **S4** & **S3** & **S4** & **S3** & **S4** \\ \hline C01 & 69 & \(-65.1\) & \(-64.5\) & 18.3 & 17.7 & 67.6 & 66.9 \\ C08 & 20 & 0.9 & 1.4 & 4.6 & 6.0 & 4.6 & 6.1 \\ C10 & 33 & \(-3.1\) & \(-9.4\) & 13.2 & 13.9 & 13.4 & 16.6 \\ C11 & 65 & \(-0.7\) & 1.0 & 4.7 & 5.5 & 4.8 & 5.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: SLR assessment of strategies 3 and 4 (unit: cm). receiver clock error, and other parameters. Thus, the precision improvement of MEO satellites is higher than that of the other types of satellites. GEO satellites are the least affected. Figure 5 shows that strategy 3 is superior to strategy 1 in terms of the along-track precision of the C01, C02, and C04 satellite. The stationary orbit of GEO satellites results in a small difference between BeiDou and GPS data for a determination of the parameters, resulting in a lower impact of the joint orbit determination on GEO satellites. On average, the precision of strategy 1 is 26.2% higher in the along-track direction, 39.8% higher in the cross-track direction, and 50% higher in the radial direction than strategy 3. However, the statistics involve GEO satellites. To better illustrate the influence of joint orbit determination on each direction, we only account for IGSO and MEO satellites.