Wide Area Augmentation System (WAAS) test and evaluation concepts

The Wide Area Augmentation System represents an FAA major acquisition that will augment the Department of Defense's Global Positioning System (GPS). The WAAS has the potential to reduce costs and improve capability by eventually replacing less efficient navigation and landing aids. The WAAS will provide augmentation to the basic GPS architecture improving accuracy, integrity, availability, and continuity of service for en route aircraft navigation to CAT I precision approaches within a specified service volume. The system architecture makes use of Geostationary Satellites, or GEOs. The GEOs transmit on L1 to enable GPS receivers to perform pseudoranging. In addition, the GEOs will include information in the message frame that contains differential correction, ionospheric delay estimates, and clock corrections. The collected and processed information originates from a ground network of reference stations that monitor the ionospheric and tropospheric conditions in their local vicinities and receive inputs from a highly accurate time baseline. The purpose of this paper is to describe the WAAS concepts, and the FAA's approach to Test and Evaluation on the program. The strategy for implementing the WAAS into the National Airspace System (NAS), and what constitutes a NAS element and NAS subsystem are discussed.