Availability Aspects of a Terrain Database Integrity Monitor

Jacob Campbell, Maarten Uijt de Haag and Robert Gray

Abstract:	This paper discusses methods that can be used to determine the availability of real-time database integrity monitors in Synthetic Vision Systems (SVS). As part of NASA’s aviation safety program, Ohio University has been developing a prototype SVS that includes a terrain database integrity monitor. This prototype SVS consists of a perspective display provided by Delft University, driven by a Honeywell navigation grade Inertial Navigation System (INS), Differential GPS (DGPS), Digital Terrain Elevation Data (DTED 0 and DTED 1), and a Honeywell radar altimeter. When utilizing a terrain elevation database in an SVS application that is of higher criticality than advisory it may be necessary to include a terrain database integrity monitor to achieve the required levels of integrity. Ohio University is currently developing a prototype integrity monitor for terrain databases. In Ohio University’s integrity monitor scheme, information from a DGPS sensor and radar altimeter is combined to generate a synthesized elevation profile. This synthesized profile is then compared to the stored elevation profile. If there are inconsistencies between the two profiles, an integrity alarm will be generated and presented to the pilot in some fashion. For the proposed integrity monitor to work, it is assumed that the terrain-profile below the aircraft has a certain degree of uniqueness. In absence of such uniqueness, certain errors may remain undetected by the integrity monitor. An example scenario would be the presence of horizontal errors in a terrain lacking undulations. In these cases, the integrity function is said to be not available. This paper addresses the integrity monitor availability issue and presents simulation results that illustrate the dependency of the integrity monitor availability on the terrain-type under the aircraft. SVS integrity monitor data collected from flight tests will also be used to verify the simulated results.
Published in:	Proceedings of the 57th Annual Meeting of The Institute of Navigation (2001) June 11 - 13, 2001 Albuquerque, NM
Pages:	770 - 777
Cite this article:	Campbell, Jacob, de Haag, Maarten Uijt, Gray, Robert, "Availability Aspects of a Terrain Database Integrity Monitor," Proceedings of the 57th Annual Meeting of The Institute of Navigation (2001), Albuquerque, NM, June 2001, pp. 770-777.
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