Wide area augmentation of the Global Positioning System

TLDR

The Wide Area Augmentation System (WAAS) is being deployed by the FAA to augment the Global Positioning System (GPS). WAAS is intended to enhance GPS by providing three services: improved integrity, accuracy, and availability. WAAS broadcasts spread‑spectrum ranging signals from communication satellites, incorporates them into airborne receivers, uses a nationwide ground network to monitor satellite health and modulate integrity and correction data onto the signals, and delivers accuracy corrections that reduce GPS error from ~100 m to 8 m. The augmented system reduces sensitivity to component failures, improves time availability and continuity, and will serve as the primary navigation system for aircraft across oceanic, domestic, metropolitan, and airport‑approach airspaces.

Abstract

The Wide Area Augmentation System (WAAS) is being deployed by the Federal Aviation Administration (FAA) to augment the Global Positioning System (GPS). The WAAS will aid GPS with the following three services. First, it will broadcast spread-spectrum ranging signals from communication satellites. The airborne WAAS receiver will add these new ranging signals to the GPS constellation of measurements. By so doing, the augmented position fix will be less sensitive to the failure of individual system components, thus improving time availability and continuity of service. Second, the WAAS will use a nationwide ground network to monitor the health of all satellites over our airspace and flag situations which threaten flight safety. This data will be modulated on to the WAAS ranging signals and broadcast to the users, thereby guaranteeing the integrity of the airborne position fix. Third, the WAAS will use the ground network to develop corrections for the errors which currently limit the accuracy of unaugmented GPS. This data will also be included on the WAAS broadcast and will improve position accuracy from approximately 100 m to 8 m. When complete, the augmented system will provide an accurate position fix from satellites to an unlimited number of aircraft across the nation. It will be the primary navigation system for aircraft in oceanic routes, enroute over our domestic airspace, in crowded metropolitan airspaces, and on airport approach.