Which statement correctly describes WAAS?

• A. A ground-based augmentation system for radar.
• B. A differential GPS system that improves accuracy by transmitting corrections to airborne GPS receivers.
• C. A satellite navigation system replacement.
• D. An autonomous onboard navigation algorithm.

Answer: (B)

WAAS is a satellite-based augmentation system that provides corrections to GPS signals to improve accuracy, integrity, and availability for users, including airborne receivers. It works by using a network of ground reference stations to monitor GPS, feeding data to a processing center, which generates corrections and integrity information that are broadcast to users via geostationary satellites. This description fits a differential GPS-like system that sends corrections to airborne GPS receivers, which is why it’s the best way to describe WAAS. It isn’t a ground-based radar augmentation, it isn’t a replacement for GPS, and it isn’t an autonomous onboard navigation algorithm.