Receiver autonomous integrity monitoring

Receiver autonomous integrity monitoring (RAIM) is a technology developed to assess the integrity of individual signals collected and integrated by the receiver units employed in a Global Navigation Satellite System (GNSS). In U.S. pilot guidance, the FAA describes RAIM as a GPS receiver capability for self-integrity monitoring to ensure available satellite signals meet integrity requirements for a given phase of flight.

Source: Wikipedia — Receiver autonomous integrity monitoring (CC BY-SA 4.0)