Fault Detection and Elimination for Galileo-GPS Vertical Guidance

In anticipation of the future launches of dual-frequency GNSS satellites, such as Galileo and GPS block III, a series of new developments has taken place in the field of Receiver Autonomous Integrity Monitoring (RAIM). Of particular interest were the topics of multi-constellation RAIM and analyzing the impact of multiple simultaneous ranging failures. Given the expected increase in the number of ranging sources for the aviation user, a breakthrough is expected to be made in the use of satellite navigation for precision approaches and other critical operations. The reduction in nominal error bounds by removal of the ionospheric delay term from the measurements, together with the presence of a larger number of satellites is going to increase the robustness against satellite failures and hazardous pseudorange errors. Vertical errors are critical during aviation precision approaches, and they are also generally greater than horizontal errors for satellite-based positioning. The purpose of this work is to investigate what Vertical Protection Level (VPL) values could be achieved with an unaided combined Galileo-GPS constellation under conservative failure assumptions. The foundations that enable the methods developed in this paper have already been laid in previous work [2] by identifying a viable RAIM algorithm for monitoring dual-frequency ranging signals and conducting detailed parametric studies to identify what threat space needs to be covered with future