How is GPS integrity monitored for aviation applications?

GPS integrity ensures position errors don't exceed tolerable limits for the operation. Monitoring methods: RAIM (Receiver Autonomous Integrity Monitoring) - uses redundant satellite measurements to detect and exclude faulty satellites (requires 5 satellites for detection, 6 for exclusion); WAAS/SBAS - ground stations monitor satellites and broadcast corrections with integrity data; GBAS - local ground monitoring for precision approach; and ARAIM (Advanced RAIM) - uses dual-frequency/multi-constellation for improved availability. Integrity requirements define: Alert limit (maximum allowable error), Time-to-alert (how quickly fault must be detected), and Integrity risk (probability of undetected error). LPV approaches require 99.999% integrity level.