# Development Status and Service Performance Preliminary Analysis for BDSBAS
## 4 BDSBAS Service Performance Evaluation
### SF Service Integrity and Availability  
According to the performance specifications of ICAO Annex 10 for APV-I approach, the HAL and VAL are 40 m and 50 m, respectively, and the horizontal and vertical accuracy thresholds (95%) are required to be above 16 m and 20 m, respectively. The position errors and position protection levels are calculated with the monitoring receiver observations from 1 July to 10 July in 2020. The horizontal integrity and vertical integrity are assessed by the accumulate Stanford diagrams and shown in Figures 7 and 8, respectively. Stanford diagram outlines the key concepts related to integrity. The X-axis represents the position error and the Y-axis represents the protection level. The misleading information (MI) is defined as when the position error exceeds the protection level but is still less than the required alert limit of the system. If the protection level is less than the alert limit while the position error exceeds the alert limit, it is labelled as hazardously misleading information (HMI). When this occurs, the user is in a potentially dangerous situation as the system is providing dangerous information to the user who is unaware. The integrity risk is the probability that a position error is larger than the alert limit without any alert. If the protection level is less than the system alert limit and the position error is less than the protection level, then the system is available and operating within its normal bounds. If  
\begin{table}
\begin{tabular}{l 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\%)**} & & **(95\%)** & & **Rcv ID** & \multicolumn{2}{c}{**(95\%)**} & \multicolumn{2}{c}{**(95\%)**} \\ \cline{2-9}  & **BDSBAS + BDS** & **BDS** & **BDSBAS + BDS** & **BDS** & & **BDSBAS + BDS** & **BDS** \\ \hline
1 & 0.558 & 0.765 & 1.050 & 1.176 & 16 & 0.677 & 0.931 & 1.237 & 1.377 \\ \hline
2 & 0.365 & 0.642 & 0.733 & 1.079 & 17 & 0.741 & 0.928 & 1.263 & 1.469 \\ \hline
3 & 0.571 & 0.758 & 1.140 & 1.485 & 18 & 0.552 & 0.844 & 1.025 & 1.392 \\ \hline
4 & 0.547 & 0.748 & 1.186 & 1 the protection level has exceeded the alert limit, the system service cannot be trusted even though the position error may be acceptable. Figure 8: Vertical integrity assessment with Stanford diagram. No misleading information (MI) and no hazardous misleading information events exist. The 99.8025% testing epochs are operating within their normal bounds in vertical direction according to APV-I approach requirement. Figure 7: Horizontal integrity assessment with Stanford diagram. No misleading information (MI) and no hazardous misleading information events exist. The 99.9375% testing epochs are operating within their normal bounds in horizontal direction according to APV-I approach requirement. It is noted that no integrity risk event occurred during the whole test interval. The availability percentages of the integrity service are about 99.9% and 99.8% in the horizontal and vertical directions, respectively. To illustrate the detail relation between the protection level and the position error, the 24 h time series of position errors and the corresponding protection levels are shown in Figure 9 at the Beijing station. HPE and HPL are shown in the top subgraph and VPE and VPL are presented in the bottom subgraph. The unit of the X-axis is hours and of the Y-axis is meters. The blue lines indicate position error and the black lines indicate protection level. It shows that the protection level can envelope the position error with 100% confidence, which means that there is no integrity risk event. If the position error is less than the system accuracy threshold as well as the integrity service is under normal operation, the system service is considered available.