Mini Lesson: WAAS vs RAIM

WAAS vs RAIM: Quick Facts

RAIM (Receiver Autonomous Integrity Monitoring)

▪️Uses satellites to monitor GPS integrity

▪️Requires at least 5 satellites

▪️Monitors reliability of GPS signal

▪️Can detect errors and alert the pilot but does not correct them

▪️Sometimes needed in GPS systems without WAAS

WAAS (Wide Area Augmentation System)

▪️Uses satellites + ground stations

▪️Ground stations correct GPS errors, satellites send corrected data to the aircraft

▪️Improves GPS accuracy to about 1–2 meters

▪️Provides built-in integrity monitoring, so RAIM is normally unnecessary

-Mountainous or remote terrain could interfere with signal making WAAS unreliable

▪️Allows more precise approaches (LPV, LNAV/VNAV)

🔑Key Takeaways🔑

▪️RAIM only monitors for errors, WAAS monitors and corrects them

▪️RAIM relies on satellites while WAAS relies on both satellites and ground stations

▪️WAAS improves GPS accuracy to 1-2 meters

▪️Not all GPS systems are WAAS capable