Advanced Receiver Autonomous Integrity Monitoring (ARAIM) based on multi-constellation GNSS would enable aircraft to perform LPV-200 precision approaches by autonomously detecting and excluding faults without an aid of GNSS augmentation systems. In view of that, ARAIM is emerging as a new concept of the next generation precision navigation system. The user computes Vertical Protection Levels (VPL) and Horizontal Protection Levels (HPL) that satisfies the integrity requirement of the ARIAM system using the standard deviations of GNSS error sources. Among the error sources, the Signal-In-Space (SIS) range error, which include GPS ephemeris and clock errors, dominates the magnitude of the user confidence bounds in position domain. The SIS error is represented with User Range Accuracy (URA), which is a conservative one sigma (standard deviation) value. This paper defines SIS error metrics and analyzes the performance of these metrics. The bottom-up method computes the SIS errors using broadcast navigation message from IGS International GNSS Service (IGS) and precise ephemerides/clocks provided by National Geospatial-Intelligence Agency (NGA). The result from this study is expected to help design the ARAIM architecture and assess its performance in the future.

Keywords: signal-in-space errors, ARAIM (advanced receiver autonomous integrity monitoring)