GNSS RAIM Availability Assessment for Worldwide Precision Approaches

The number of satellites in Global Navigation Satellite System (GNSS) will be increased greatly for the launch of Galileo and Compass satellites. Receiver Autonomous Integrity Monitoring (RAIM) is expected to provide better guidance for aircraft approaching airports and landing, while the unaided GPS with RAIM provide hundreds meters in Horizontal Protection Level (HPL) nowadays. Firstly, different RAIM algorithms are analyzed in this paper and the algorithm free of weighting matrix is proposed to calculate protection levels. Secondly, the mathematical model for availability assessment is presented. Finally, the paper gives simulation results using dual frequency signals and GPS+Galileo constellations.The results show that the RAIM availability is no less than 99.5% in worldwide regions for LPV 200 and APV I, and GNSS with RAIM yields the Vertical Protection Level (VPL) under 25 meters for nominal operations.