Impact of geometry sensitive satellites on the navigation performance of ground-based augmented GPS

This paper discussed the impact of geometry sensitive of satellites on the navigation performance of ground-based augmentation system (GBAS). The nominal number of satellites (space vehicles, or SVs), defined in RTCA/DO-229E, in the global positioning system (GPS) constellation was used in the analysis. In the quantification of GBAS navigation performance (i.e., the protection level or PL computed at aircraft), full constellation and one and two SV outage scenarios were applied through the search process within all combinations of healthy SV geometries (i.e., subsets of SVs in view). It was observed that some SV combinations, subset geometries obtained after depletion of constellation reduced GBAS navigation performances significantly. These geometries were treated as unsafe for an initiation of intended aircraft precision approach and landing. Further, SVs affecting the integrity and the availability of GBAS in this manner were identified as 'geometry sensitive'. The impact of geometry sensitive SVs on the GBAS navigation performance were quantified and ranked per outage cases.