## 3 Experiments and Discussions
### Accuracy of Real-Time Vehicle-Borne PPP
\begin{table}
\begin{tabular}{c c} \hline \hline
**Item** & **Processing Strategies** \\ \hline GNSS & BDS-3 and GPS \\ Signal selection of IF PPP & B1I+B2b \\  & GPS: L1+L2 \\ Signal selection of SF PPP & BDS-3: B2b \\ GPS: L1 \\ Interval & 1 s \\ Cutoff angle & 10\({}^{\circ}\) \\ Weight method & Elevation angle dependent \\ Troposphere & Estimate the wet component \\  & IF PPP: IF combination \\ Ionospheric & SF PPP: Estimated \\ PCO/PCV & IGS14.txt \\ Ambiguity & Estimated \\ Adjustment & Sequential least square \\ Satellite DCB & Corrected by DCB products \\ Receiver DCB & IF PPP: IF combination \\  & SF PPP: Estimated \\ \hline \hline \end{tabular}
\end{table} 
Table 7: PPP processing strategies of dynamic test. Figure 13: Number of visible satellites and PDOP values during the dynamic test. Figure 14: Time series of position errors of the dual-(**a**)/single (**b**)-frequency vehicle-borne RT-PPP using different SSR products. The accuracies in terms of RMSE of vehicle-borne dual-frequency PPP and single-frequency PPP based on different SSR products are shown in Tables 8 and 9. For the dual-frequency PPP, the positioning accuracy of the BDS-3 B1I+B2b PPP using PPP-B2b SSR products is 35.8 cm, 55.0 cm, and 121.3 cm in the E, N, and U components, respectively. In contrast, the B1I+B2b PPP positioning accuracy using CAS products is the highest in horizontal with 58.9 cm, and WHU products are the highest in 3D with 129.7 cm. The solutions based on broadcast ephemeris (67.5 cm and 182.4 cm in horizontal and 3D components) have the worst positioning accuracy among the seven products. The GPS L1+L2 PPP is 57.0 cm, 47.9 cm, and 101.4 cm in the E, N, and U components. The GPS L1+L2 PPP solution has the highest 3D accuracy (126.0 cm) and the worst horizontal accuracy (74.5 cm) compared to the BDS-3 B1I+B2b PPP using the SSR product of both PPP-B2b and IGS RTS. For the single-frequency PPP, the positioning accuracy of B2b frequency PPP based on PPP-B2b products in E, N, and U components are 87.1 cm, 32.9 cm, and 103.5 cm, respectively; those positioning accuracies of GPS L1 PPP are 42.3 cm, 47.8 cm, and 63.9 cm, respectively. While using GPS, the positioning accuracy is slightly higher in horizontal components (42.3 cm and 47.8 cm) but much worse in the U direction (129.2 cm). For the solutions based on IGS RTS real-time products, the positioning accuracy using GFZ real-time products is the best, with 75.9 cm and 96.8 cm in horizontal and 3D components, respectively. The positioning accuracy with WHU real-time products is 175.7 cm and 250.5 cm in horizontal and 3D components, respectively, which are the worst among other real-time products. In Figure 14, a noticeable systematic error exists in the N and U components, which are caused by the unabsorbed satellite clock errors. Compared to BDS-3 B1I+B2b PPP, the BDS-3 B2b PPP provides smoother position solutions, especially after satellites signal re-tracking, which is caused by the greater noise of the dual-frequency IF and high-accuracy of prior ionosphere data used in single-frequency PPP. Figure 15 shows the radial, along-track, and cross-track RMS values of the orbit's errors and clock STD values for each type of real-time product, as well as the positioning accuracy of static and dynamic with single/dual-frequency PPP. In static PPP, the IGS real-time product positioning accuracy is better than that of PPP-B2b, and BRDC positioning accuracy is the worst among the seven products. This is consistent with the orbit and clock accuracies of each real-time product. In dynamic PPP, affected by the complex positioning environment, the positioning accuracy of various products is similar.