WAAS improvements are achieved by which type of system?

• A. Autonomous GPS.
• B. Differential GPS.
• C. Inertial navigation.
• D. Radio navigation.

Answer: (B)

WAAS improvements come from applying Differential GPS corrections. A network of ground reference stations monitors GPS signals across the region to detect errors in satellite orbit (ephemeris) and ionospheric delays. Those measurements feed a master station that computes corrected pseudorange values and ionospheric models, and the corrections are broadcast to users via geostationary satellites. Receivers apply these corrections to improve accuracy, integrity, and availability. This is a Differential GPS augmentation system, not autonomous GPS (which would rely only on the receiver’s signals), not inertial navigation (which uses motion sensors), and not traditional radio navigation (VOR/LOC/TACAN).