# GPS + BDS Network Real-Time Differential Positioning Using a Position Domain Estimation Method
## 3 Results
### Static Experiment
#### 3.1.2 Data Set II  
Figure 6 shows the position errors of the network real-time differential positioning and the number of observed satellites for station ZQGT. The position errors of PD fluctuate less than those of RD. For both PD and RD, the position errors of GPS + BDS solution are smaller than those of GPS-only solution. This is consistent with the results in Figure 3. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & & \multicolumn{3}{c}{**GPS**} & \multicolumn{3}{c}{**GPS + BDS**} \\ \cline{3-10}  & & **N** & **E** & **U** & **N** & **E** & **U** \\ \hline \multirow{4}{*}{Inside} & RD (m) & 0.738 & 0.442 & 1.268 & 0.275 & 0.247 & 0.615 \\  & PD (m) & 0.380 & 0.266 & 0.714 & 0.190 & 0.209 & 0.414 \\  & Improvement (\%) & 48.6 & 39.8 & 43.7 & 31.0 & 15.2 & 32.7 \\ \hline \multirow{4}{*}{Outside} & RD (m) & 0.713 & 0.472 & 1.186 & 0.241 & 0.237 & 0.852 \\  & PD (m) & 0.394 & 0.281 & 0.736 & 0.161 & 0.153 & 0.439 \\  & Improvement (\%) & 44.8 & 40.5 & 37.9 & 33.0 & 35.3 & 48.5 \\ \hline \multirow{4}{*}{All} & RD (m) & 0.728 & 0.463 & 1.230 & 0.265 & 0.242 & 0.745 \\  & PD (m) & 0.390 & 0.282 & 0.733 & 0.188 & 0.187 & 0.437 \\ \cline{1-1}  & Improvement (\%) & 46.4 & 39.1 & 40.4 & 29.0 & 22.6 & 41.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: STD values of the network real-time differential positioning for the inside, the outside and all user stations. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & & \multicolumn{3}{c}{**N**} & \multicolumn{3}{c}{**E**} & \multicolumn{3}{c}{**U**} \\ \cline{3-10}  & & \multicolumn{3}{c}{**\(\pm\)0.25 m**} & \(\pm\)**0.5 m** & \(\pm\)**1 m** & \(\pm\)**0.25 m** & \(\pm\)**0.5 m** & \(\pm\)**1 m** & \(\pm\)**0.5 m** & \(\pm\)**1 m** \\ \hline \multirow{4}{*}{Inside} & GPS & RD & 60.0 & 87.3 & 95.9 & 61.8 & 87.1 & 97.0 & 55.9 & 83.5 \\  & PD & 61.7 & 88.9 & 97.9 & 65.4 & 91.4 & 99.4 & 62.0 & 88.8 \\  & Improvement & 2.8 & 1.9 & 2.1 & 5.8 & 4.9 & 2.6 & 11.0 & 6.4 \\ \cline{2-10}  & & RD & 81.4 & 91.6 & 97.2 & 74.5 & 95.9 & 99.3 & 68.3 & 93.3 \\  & GPS + BDS & PD & 82.0 & 93.7 & 99.6 & 74.7 & 97.3 & 100.0 & 74.3 & 98.5 \\  & Improvement & 0.8 & 2.3 & 2.4 & 0.3 & 1.4 & 0.7 & 8.8 & 5.6 \\ \hline \multirow{4}{*}{Outside} & GPS & RD & 65.0 & 89.9 & 96.0 & 66.0 & 90.2 & 96.8 & 51.0 & 80.6 \\  & PD & 66.1 & 90.5 & 97.6 & 69.4 & 95.2 & 99.4 & 56.2 & 86.1 \\  & Improvement & 1.6 & 0.7 & 1.7 & 5.1 & 5.6 & 2.7 & 10.0 & 6.8 \\ \cline{2-10}  & & RD & 80.9 & 82.6 & 95.5 & 79.9 & 95.2 & 99.4 & 49.7 & 85.4 \\  & GPS + BDS & PD & 83.5 & 86.3 & 99.2 & 90.1 & 99.9 & 100.0 & 62.4 & 94.8 \\  & Improvement & 3.1 & 4.5 & 3.9 & 12.8 & 4.9 & 0.6 & 25.6 & 11.1 \\ \hline \multirow{4}{*}{All} & GPS & RD & 62.6 & 88.6 & 95.9 & 63.9 & 88.7 & 96.9 & 53.4 & 82.0 \\  & PD & 63.9 & 89.7 & 97.8 & 67.4 & 93.4 & 99.4 & 59.1 & 87.4 \\  & Improvement & 2.2 & 1.3 & 1.9 & 5.5 & 5.3 & 2.6 & 10.5 & 6.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Percentages of the position errors of the network real-time differential positioning in predefined thresholds for the inside, the outside and all user stations. (Unit: %)The position errors of GPS-only solution in this figure are significantly smaller than those in Figure 3, for both PD and RD. This is attributed to the more stable and larger number of observed GPS satellites in Data set II. In GPS + BDS solution, the difference of position error fluctuation between Figures 3 and 6 is small for PD, but large for RD. Since the sufficient number of satellites guarantees the performance of PD for both two figures, the varying number of satellites in Figure 3 restricts the performance of RD. The RMS errors of the network real-time differential positioning for each user station in Data set II are illustrated in Figure 7. Similar to Figure 4, the RMS errors of PD are smaller than those of RD, and the RMS errors of GPS + BDS solution are smaller than those of GPS-only solution. The RMS errors of GPS + BDS solution are usually smaller than 0.3 m, 0.25 m and 0.4 m in the N, E and U components, respectively.