Revisiting RAIM

Fred Simonds

Thursday, July 22, 2021 at 11:36 AM ET

Verified

Key Takeaways:

RAIM (Receiver Autonomous Integrity Monitoring) independently monitors the integrity and accuracy of GPS position fixes by detecting and, in some cases, correcting errors from various sources, ensuring reliable navigation by filling critical detection gaps.
It functions by comparing multiple satellite signals and pseudorange measurements for consistency, featuring Fault Detection (FD) and more advanced Fault Detection and Exclusion (FDE) capabilities, with FDE allowing continued operation despite a satellite fault.
Essential for pilot safety, RAIM often requires preflight checks (especially for non-WAAS systems) to confirm availability, and its integrity monitoring capabilities are significantly enhanced by the integration of WAAS technology, which provides complementary integrity signals.

See a mistake? Contact us.

Receiver Autonomous Integrity Monitoring is a mouthful, but it’s descriptive. RAIM independently assesses the integrity of positions reported by a GPS receiver.

RAIM is essential because half a dozen error sources can result in position errors ranging from negligible to unsafe. RAIM detects and, in some cases, corrects these errors. Only then can a pilot know the GPS is accurate.