# Research on the Impact of BDS-2/3 Receiver ISB on LEO Satellite POD
## 4 Results and Analysis
### GPS+BDS-2/3 Combined Orbit Solution  
Table 4 presents the IF code and phase residual statistics results of the GPS and BDS joint different strategies, as described in Section 3.2. The BDS-2 IF code and phase residuals are, respectively, about 115 cm and 1 cm for GPS+BDS-2-based POD solution and GPS+BDS-based POD solution. The BDS-3 IF code and phase residuals are, respectively, about 69 cm and 0.92 cm for GPS+BDS-3-based POD solution and GPS+BDS-based POD solution. The GPS IF code and phase residuals are, respectively, about 80 cm and 0.97 cm for each POD solution. These residuals results show that each system IF code residual from the three combined strategies is closed to the IF code residuals of the GPS-based, BDS-2-based and BDS-3-based POD. Figure 6 shows the results of both the orbit overlapping consistency and the combined orbit RMS errors compared with GPS-based POD, and Table 5 presents, respectively, the orbit RMS difference statistics. The 3D RMS differences for the orbit overlapping consistency are, respectively, 3.15 cm, 2.91 cm and 3.03 cm from the GPS+BDS-based POD solution, GPS+BDS-2-based POD solution and GPS+BDS-3-based POD solution, and the differences between them are less than 3 mm. The radial RMS differences for the orbit overlapping consistency of the three different strategies are, respectively, 0.91 cm, 0.88 cm and 0.91 cm, and the differences between them are less than 1 mm. The along and cross RMS differences for the orbit overlapping consistency of the three different strategies are, respectively, about 2.6 cm and 1.07 cm. It is important to note that the STD values of the GPS+BDS-3-based orbit overlapping consistency from all the POD arcs are smallest in the 3D, radial, along and cross directions. Figure 5: The BDS-based orbit RMS errors results compared with the GPS-based orbits. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Test**} & \multicolumn{2}{c}{**Reduced Ratio**} & \multirow{2}{*}{**3D**} & \multirow{2}{*}{**Radial**} & \multirow{2}{*}{**Along**} & \multirow{2}{*}{**Cross**} \\ \cline{2-2} \cline{5-6}  & **BDS-2** & & & & & & \\ \hline
**BDS-2-based POD** & / & / & 15.10 & 5.11 & 10.56 & 8.69 \\
**BDS-3-based POD** & 56\% & / & 6.57 & 2.29 & 5.36 & 2.74 \\
**BDS-2/3-based POD** & 61\% & 10\% & 5.92 & 2.35 & 5.02 & 2.02 \\
**BDS-2/3-B-based POD** & 64\% & 18\% & 5.37 & 1.96 & 4.28 & 2.48 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: BDS-based orbit RMS difference statistics results compared with GPS-based orbits (unit: cm). \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **TEST** & **GPS+BDS-Based POD** & **GPS+BDS-3-Based POD** & **GPS+BDS-2-Based POD** \\ \hline \multirow{3}{*}{**BDS-2**} & **IF code** & 114.96 & \(\backslash\) & 115.02 \\  & **IF phase** & 1.00 & \(\backslash\) & 1.00 \\  & **IF code** & 68.14 & 69.03 & \(\backslash\) \\  & **IF phase** & 0.91 & 0.93 & \(\backslash\) \\  & **IF code** & 79.68 & 80.42 & 79.30 \\ \multirow{3}{*}{**GPS**} & **IF phase** & 0.97 & 0.98 & 0.96 \\  & **IF code** & 85.58 & 77.59 & 89.35 \\ \multirow{3}{*}{**Entirety**} & **IF phase** & 0.96 & 0.97 & 0.97 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The IF code and phase residual statistics results of the GPS and BDS joint different strategies (unit: cm). Figure 6: The orbit RMS of the GPS and BDS combined different strategies. **(A)** The orbit RMS in overlapping consistency from GPS+BDS-based POD, GPS+BDS-2-based POD and GPS+BDS-3-based POD. **(B)**The orbit RMS between GPS-based POD and the three GPS and BDS combined POD strategies. The orbit RMS differences between the GPS+BDS-based POD solutions and GPS-based POD solutions are, respectively, 3.20 cm, 0.99 cm, 2.41 cm and 1.59 cm in the 3D, radial, along and cross directions. The GPS+BDS-2-based POD orbit RMS differences compared with the GPS-based orbit are, respectively, 3.07 cm, 0.95 cm, 2.06 cm and 1.85 cm in the 3D, radial, along and cross directions.