Abstract: A research is presented into the GPS RAIM(receiver autonomous integrity monitoring) availability of the phases of nonprecision approach and terminal navigation over China. The influences of barometric altimeter aiding and bias errors on GPS RAIM availability are analyzed. The simulation results show that the barometric altimeter GPS integration system is an effective measure for improving the GPS RAIM availability, and the large range or small range bias errors will cause small missed detection probabilities, while the middle range bias errors will cause large missed dectection probabilities.

Key words: barometric pressurealtimeters, failure　parityvectors