What does Local Area Augmentation System (LAAS) do?

• A. A satellite weather data link system.
• B. A ground-based navigation aid used for terminal area surveillance.
• C. 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.
• D. An inertial navigation alignment device.

Answer: (C)

LAAS is a ground-based augmentation to GPS that provides differential corrections to improve precision in a local area around an airport. It uses a reference station to compare GPS measurements against a known position, determines the satellite measurement errors, and transmits correction data to airborne GPS receivers. With these corrections, the aircraft’s GPS solution becomes much more accurate, enabling precise approaches (such as Category I). This is essentially a DGPS-like system that is localized rather than global, which is why it differs from satellite-based augmentations like WAAS. It’s not a weather data link, not a surveillance terminal-area navigation aid, and not an inertial alignment device.