What is RAIM prediction and when do I need to use it?
Receiver autonomous integrity monitoring (RAIM) continuously monitors and compares signals from multiple satellites to ensure GPS signal accuracy. When you fly IFR using a non-WAAS GPS as your primary navigation system you are required to do a RAIM prediction check for your route before each flight. If RAIM is predicted to be unavailable, you must use other navigation systems or delay or cancel your flight.