# Development Status and Service Performance Preliminary Analysis for BDSBAS
## 4 BDSBAS Service Performance Evaluation
### BDSBAS DFMC Service Accuracy  
The service accuracy of the BDSBAS DFMC service is similarly analyzed with 30 BDS monitoring receivers. The testing data sampling interval is 20 s. The absolute value of horizontal and vertical position errors with 95% confidence level are calculated every day and the time series of all monitoring receivers 95 th percentile position errors are displayed in Figure 5.  
In Figure 5, the lines in the top subgraph indicate the time series of horizontal position errors and the lines in the bottom subgraph show the position errors in vertical direction. Different colors indicate different monitoring receivers. The X-axis represents time in days, and the Y-axis represents position errors in meters. It shows that the variance of position errors for the same monitoring receiver is relatively stable in different days, and the position errors of all receivers are relatively consistent. The HPE of different monitoring receivers varies from 0.5 m to 1.0 m, and the VPE of different monitoring receivers varies from 1.0 m to 1.5 m. As most ionospheric delay errors can be eliminated by using dual-frequency observations, the vertical position accuracy of the BDSBAS DFMC service is significantly improved compared with the BDSBAS SF service.  
\begin{table}
\begin{tabular}{l c c c c c c c c c} \hline \hline \multirow{2}{*}{**Rcv ID**} & \multicolumn{2}{c}{**Horizontal**} & \multicolumn{2}{c}{**Vertical**} & \multicolumn{2}{c}{**Horizontal**} & \multicolumn{2}{c}{**Vertical**} \\  & \multicolumn{2}{c}{**(95\%)**} & \multicolumn{2}{c}{**(95\%)**} & \multicolumn{2}{c}{**Rcv ID**} & \multicolumn{2}{c}{**(95\%)**} & \multicolumn{2}{c}{**(95\%)**} \\ \cline{2-10}  & **BDSBAS + GPS** & **GPS** & **BDSBAS + GPS** & **GPS** & & **BDSBAS + GPS** & **GPS** & **BDSBAS + GPS** & **GPS** \\ \hline
1 & 0.769 & 1.699 & 1.837 & 2.488 & 16 & 1.129 & 1.631 & 2.662 & 3.039 \\ \hline
2 & 0.744 & 1.688 & 1.739 & 2.477 & 17 & 0.865 & 1.629 & 2.503 & 2.708 \\ \hline
3 &  
The time series of position errors are compared analyzed between the BDSBAS DFMC service and the BDS dual-frequency service and the results of one monitoring receiver are shown in Figure 6 as an example. The position errors in the north-south, east-west and vertical directions are shown in the top, middle and bottom subgraphs, respectively. The red lines indicate the BDSBAS DFMC service and the black lines represent the BDS dual-frequency service. The X-axis represents time in hours. It is noted that the position errors (95%) are 0.51 m, 0.57 m and 1.60 m in north-south, east-west and vertical directions, respectively, under BDS dual-frequency service, and the position errors (95%) are 0.25 m, 0.23 m and 0.77 m in north-south, east-west and vertical directions under BDSBAS DFMC service. The position accuracy of the BDSBAS DFMC service is also clearly improved compared with the BDS dual-frequency service.  
Figure 5: Time series of 95 th percentile position errors of 30 monitoring receivers under BDSBAS DFMC service. One color represents one receiver.  
Figure 6: Comparison of position errors between the BDSBAS DFMC service (red lines) and the BDS dual-frequency service (black lines).  
The average value of 95% absolute value of position errors of 10 days is calculated to represent the position accuracy of the monitoring receiver. The position accuracies of 30 monitoring receivers under the BDSBAS DFMC service and the BDS dual-frequency service are comparatively analyzed and the statistics results are listed in Table 3.  
The results show that the horizontal and vertical position accuracies of 30 monitoring receivers are less than 1.0 m and 1.5 m, respectively, under BDSBAS DFMC service. The average values of the 30 monitoring receivers' position accuracies in horizontal and vertical directions are about 0.6 m and 1.2 m, respectively, which are improved by about 25% and 20% compared with BDS dual-frequency service.