Which statement best describes LAAS in navigation?

• A. A satellite weather data link system.
• B. A differential global positioning system (DGPS) that improves the accuracy by determining position error from the GPS satellites, then transmitting the error, or corrective factors, to the airborne GPS receiver.
• C. A ground-based navigation aid used for terminal area surveillance.
• D. An inertial navigation alignment device.

Answer: (B)

LAAS, Local Area Augmentation System, is a ground-based augmentation that improves GPS performance in a localized area around an airport so aircraft can use GPS for precision approaches. It works by having a reference station monitor GPS signals, determine the position error, and then transmit those corrections (or corrective factors) and integrity information to airborne GPS receivers in the area. In practice, this is a differential GPS-like system tailored for aviation, delivering real-time corrections to the aircraft so the GPS position is more accurate and reliable during approaches.

This isn’t a weather data link, it isn’t a radar-based surveillance aid, and it isn’t an inertial navigation alignment device.