## 5 Orbit Evaluation
### Comparison with External Products  
We conducted a comparative analysis of our BDS-3 3-day arc B1I/B3I orbit results with CODE MGEX (COM) products, as illustrated in Figure 8. Additionally, the results of comparing B1C/B2a orbits are depicted in Figure 9. The RMS values for each BDS-3 satellite orbit compared with CODE MGEX products exhibit a similar level for the B1I/B3I solutions and B1C/B2a solutions. Notably, the RMS values for every MEO SECM satellite orbit are comparable, with most SECM satellites displaying RMS values within 2 cm. The  
\begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**RMS [cm]** & **Constellation** & **Radial** & **Along-Track** & **Cross-Track** & **1D** \\ \hline B1I/B3I & All & 1.61 & 2.15 & 1.92 & 1.91 \\  & IGSO & 2.92 & 2.93 & 3.63 & 3.18 \\  & MEO CAST & 1.47 & 2.22 & 1.77 & 1.85 \\  & MEO SECM & 1.07 & 1.65 & 1.25 & 1.35 \\ \hline B1C/B2a & All & 1.58 & 2.09 & 1.86 & 1.86 \\  & IGSO & 2.87 & 2.88 & 3.37 & 3.05 \\  & MEO CAST & 1.43 & 2.16 & 1.74 & 1.80 \\  & MEO SECM & 1.04 & 1.57 & 1.24 & 1.30 \\ \hline \hline \end{tabular}
\end{table}
Table 6: The RMS of orbits overlapping for BDS-3 all satellites on radial component, along component, cross component, and 1D component, respectively.  
Figure 7: The RMS of overlapping orbits for BDS-3 of every satellite from B1C/B2a observations in radial direction, along direction, cross direction, and 1D direction, respectively.  
majority of BDS-3 MEO satellite orbits exhibit RMS values lower than 3 cm. However, C45 and C46 satellites stand out with larger RMS values, likely due to fewer tracking stations for these two satellites. The mean 1D RMS of BDS-3 for MEO satellite orbits is 2.07 cm, and for IGSO satellite orbits it is 3.79 cm when using the B1C/B2a combination. These RMS values are slightly larger than the orbits from the B1I/B3I combination, possibly because the CODE MGEX BDS-3 orbits also utilize B1I/B3I combination observations.  
Figure 8: The RMS of 3-day arc orbit comparing with CODE MGEX products for BDS-3 for every satellite from B1I/B3I observations.  
Figure 9: The RMS of 3-day arc orbit compared with CODE MGEX products for BDS-3 every satellite from B1C/B2a observations.  
The RMS values for the results of the BDS-3 B1I/B3I solution and B1C/B2a solution, encompassing both 1-day and 3-day arc comparisons with CODE MGEX products, are presented in Table 7. Notably, the 3-day arc orbits, both for the BDS-3 B1I/B3I solution and the BIC/B2a solution, exhibit an improvement of approximately 25% compared with the 1-day arc when compared with CODE MGEX orbit products. BDS-3 orbits based on B1I/B3I combinations demonstrate better consistency with the CODE MGEX orbits compared with those using the B1C/B2a combination. This may arise from the fact that CODE MGEX BDS-3 orbits also incorporate B1I/B3I combination observations. The 1D accuracy of BDS-3 orbits, including IGSO satellites and MEO satellites, is 2.35 cm when using the B1C/B2a combination in comparison with the CODE MGEX orbits. In detail, the 1D accuracy of the IGSO satellite orbit is 3.73 cm. The 1D orbit accuracy for the MEO CAST satellite is 2.27 cm and that for the MEO SECM satellite is 1.78 cm.