Optimizing the evaluation of estimation algorithm about the fault detection and exclusion (FDE) in the WAAS

The definition of the Fault Detection and Exclusion (FDE) is a receiver processing scheme that autonomously provides integrity monitoring for the position solution, using redundant exclusion (RTCA DO-229C). The FDE algorithm played a very important role in the Wide Area Augmentation System (WAAS). When the WAAS was not available, the algorithm of the FDE could provide the monitored information for the navigation position solution. Moreover it could autonomously provide the integrity monitoring for the position solution in the complicated situation. And it had a capability to detect and prevent a positioning failure which affected the navigation. The goal of the work presented in this paper was to develop an appropriately optimum evaluation of estimation methodology for assessing the integrity risk in the WAAS. A Root Mean Square Deviation (RMSD) method was employed in detecting and isolating the outlying measurements for the satellite ephemeris error and the satellite clock error. After the RMSD was deployed, another method was used to detect and isolate the fault of the satellite ephemeris error and clock error. It was that the Chebyshev law of large number combined with the Kalman filter. Therefore this algorithm could provide more precise integrity parameters of the satellite ephemeris error and clock error. It was employed to estimate the User Differential Range Error (UDRE) value by using the concepts of the false alert and the missed alert. The UDRE value was estimated by adopting the Root Mean Square Error (RMSE), the Average Euclidean Error (AEE) and the Harmonic Average Error (HAE). So it could enhance the capability of the fault tolerance and the robustness on the navigation system through providing the appropriate UDRE value.