Integrlty Monitorlng of the Global Positioning System Using a Barometrlc Altimeter

Alison Brown, Tom Schmid

Abstract:	The Global Positioning System (GPS) is a satellite based navigation and positioning system which will become fully operational in the 1990's. It will provide global, continuous navigation service with an accuracy of 100 m to an unlimited number of users. While the accuracy of GPS meets the FAA requirements for en-route, terminal and non-precision approach navigation, there are other requirements, namely coverage, reliability, availability and integrity, where the GPS does not fare so well. With particular reference to integrity (the ability of the system to notify users when the system is out of tolerance)1 the GPS system as it is now configured does not give adequately timely warning when the system accuracy falls below specification. The FAA is currently exploring techniques for ensuring the integrity of the GPS (see Ref. 4). One possibility is to establish an independent ground-based monitoring network which would broadcast a GPS integrity message. The technical issues involved with this technique are straightforward1 however the implementation would prove very costly. Another possibility is to make use of redundant information from the GPS satellites with Receiver Autonomous Integrity Monitoring (RAIM). With Receiver Autonomous Integrity Monitoring (RAIM)1 the receiver makes use of redundant satellite data to determine the integrity of the navigation solution. However, with the 18 satellite GPS constellation, there is seldom sufficient redundancy available from the satellites for RAIM to be effective. This report examines the feasibility of usin$" a Barometric Altimeter to aid the GPS receiver in monitoring the integrity of the GPS navigation signals.
Published in:	Proceedings of the 1988 National Technical Meeting of The Institute of Navigation January 26 - 29, 1988 Santa Barbara, CA
Pages:	245 - 253
Cite this article:	Brown, Alison, Schmid, Tom, "Integrlty Monitorlng of the Global Positioning System Using a Barometrlc Altimeter," Proceedings of the 1988 National Technical Meeting of The Institute of Navigation, Santa Barbara, CA, January 1988, pp. 245-253.
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