RAIM AVAILABILITY FOR GPS AUGMENTED WITH BAROMETRIC ALTIMETER AIDING AND CLOCK COASTING.

In late 1991, the FAA formed a group called the Satellite Operational Implementation Team to accelerate the introduction of satellite navigation and communications into the National Airspace System (NAS). Since then, the team has been addressing major technical and operational issues that need to be resolved before GPS is used in instrument flight rules (IFR) operations in the NAS. One of the most critical criteria for the operational approval of near-term use of GPS in the NAS is availability of receiver autonomous integrity monitoring (RAIM) detection and identification functions. To improve RAIM availability, SOFT members suggested that relatively simple GPS augmentations in the form of barometric altimeter aiding and clock coasting be considered. This paper analyzes GPS RAIM availability with these augmentations and presents the technical analyses used by the team to support its recommendations.