Implementation of a RAIM Monitor in a GPS Receiver and an Integrated GPS/IRS

Abstract

Honeywell has developed a sensor unit (GPSSU) and an integrated GPS/IRS (GPIRU) complying with the 743 and 704 ARINC standards for commercial avionics. A snap shot RAIM integrity monitor based on the parity space concept has been developed and is an integral part of these systems. This article discusses the algorithm and the implementation of the algorithm in the GPSSU and GPIRU. It considers the interface between the monitor and other equipment such as Flight Management Computer and navigation filters as well as testability. The ability of the snap shot RAIM monitor to isolate a failing satellite when the geometry allows will also be discussed. Results from simulation and tests of prototype equipment are presented. The predicted coverage in terms of detection and isolation for a 24 satellite constellation using the RAIM algorithm is included and related to current and future FAA requirements.