Differential RAIM and relative RAIM for orbit ephemeris fault detection

This paper introduces new monitors for the detection of orbit ephemeris faults affecting differential carrier phase measurements in a shipboard aircraft landing application. Two shipboard monitors are first designed. While they provide high detection performance against two targeted fault types, they are ineffective against the other types of orbit ephemeris faults. In response, to protect the user against the entire threat space, a new airborne receiver autonomous integrity monitoring (RAIM) algorithm is developed. This `unified´ RAIM approach (URAIM) exploits both differential RAIM (which is most efficient at airship separation distances larger than 5 nmi) and relative RAIM (which, in contrast, performs better as the aircraft approaches the ship). Performance evaluations demonstrate URAIM´m potential to detect all types of orbit ephemeris faults using a single, unified residual-based RAIM method.