Implementation of a GPS Integrity Anomaly Database

John W. Lavrakas, Brian J. Carroll, Karen Van Dyke and Seth A. Hieronymus

Abstract:	GPS is used worldwide for numerous applications, many of which involve safety of life. These applications not only have strong expectations for the accuracy of the GPS positioning and timing service, but for the reliability of the service as well. GPS integrity anomalies, that is unreported anomalous behaviors affecting user performance, need to be understood so users may properly design systems and services that can take advantage of GPS, yet not be adversely affected by these anomalous behaviors. In order to improve service to GPS users through enhanced capabilities, monitoring, and operations, an understanding of the failure modes is needed. This involves knowing how the failures manifest themselves, their impact on users, and assessing their probability of occurrence. To this end, the Interagency GPS Executive Board (IGEB) has funded an interagency military and civilian Integrity Failure Modes and Effects Analysis (IFMEA) project. The main objectives of the IFMEA project are to identify and understand GPS integrity requirements, examine GPS failure data in order to identify integrity failure modes, examine the causes and effects of the failures as well as their probability of occurrence, determine the impact of integrity anomalies on users, and recommend preventive action. The IFMEA project.s focus is on integrity anomalies due to space vehicle (SV) and Operational Control Segment (OCS) failures. In support of this effort, the IFMEA project has established a GPS Integrity Anomaly Database (GIAD) that summarizes known anomalies and reported impact on users. Data used to populate the database is provided by numerous government and non-government organizations worldwide. Because of this significant participation of organizations, a wide base of GPS users is incorporated, and the GIAD can provide a fairly thorough assessment of the user effect of GPS integrity anomalies which have been observed and reported. In one sense, the GIAD is both a tool and a process. The GIAD process involves collecting anomaly incident reports from participating organizations and certifying them for inclusion in the database. The archived data can be used in studies of historical trends. The database records the start and stop times of each anomaly, duration, satellite block affected, type of anomaly, and magnitude of the anomaly. The GIAD tool provides ready access to the data for government and non-government users, according to the level of information they require and are permitted to access. This paper describes the process for implementing the GIAD, including acquiring and reconciling anomaly information from various monitoring and service organizations and for posting the data for use. It also describes the core capabilities of the GIAD tool, and current status in implementing the GIAD.
Published in:	Proceedings of the 60th Annual Meeting of The Institute of Navigation (2004) June 7 - 9, 2004 Dayton Marriott Hotel Dayton, OH
Pages:	88 - 96
Cite this article:	Lavrakas, John W., Carroll, Brian J., Van Dyke, Karen, Hieronymus, Seth A., "Implementation of a GPS Integrity Anomaly Database," Proceedings of the 60th Annual Meeting of The Institute of Navigation (2004), Dayton, OH, June 2004, pp. 88-96.
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