GNSS Signal in Space Outliers Analysis Based on Historical Navigation Data

Outlier detection and isolation is critical for aviation navigation. For GNSS, outlier occurred in SIS segment is dominant to lead positioning failure. This paper proposes a historical data based methodology for the analysis of SIS range outliers. Historical SIS outliers are collected by comparing broadcasted ephemeris with precision ephemeris provided by IGS. SIS range outliers are computed around China's airspace. Both the spatial and temporal characteristics of outliers are carefully discussed. Outlier duration, magnitude and influenced area are considered as the most important parameters for the outlier pool establishment. The relationship between outliers and influenced aviation phase of LPV200 is also studied, with ICAO'S required navigation performance as criteria. Ten years' GPS data is used for experiments. The results show that temporal outliers are closely related to the outlier duration, spatial outliers are mainly linked to the outlier magnitude. With year increases from 2002 to 2010, total number of ephemeris outliers decreases. What's more, ephemeris outliers have significant influence on LPV200 performance. When the magnitude of outlier is large enough, the 99.999% availability is hardly meet with by current technical framework. Our work is valuable not only for GNSS integrity performance assessment and also brings benefits to the development of enhance integrity monitor system in near future.