Test Results of GPS Based Attitude Determining System for Marine Navigation

Debra L. Diefes, Geoffrey G. Hazel, and Darrell F. Greenlee

Abstract:	Under contract with the U.S. Coast Guard, Adroit Sys- tems, Inc. has developed a low cost, GPS based Atti- tude Determining System (ADS) for marine navigation, TRIADSTM . The Coast Guard will use the system for general navigation, as well as hydrographic surveying, ice breaker navigation, and positioning buoys or other objects. Following a successful system demonstration validating the concept design, a system has been developed and tested. The ADS navigation system makes use of the full vis- ible satellite constellation. This allows the GPS based attitude determining system to be designated as a pri- mary navigation sensor. Approval for GPS ADS as a primary navigation system can be pursued now that the constellation is complete. The full constellation also allows the optimum satellite constellation to be selected based on the attitude of a platform. Having more than the required number of satellites available not only enhances system accuracy and robustness, but it also enables the system to perform integrity checks in the form of receiver autonomous integrity monitoring @AIM). The Coast Guard is currently studying integrated nav- igation systems, the ECDIS (Electronic Chart Display and Information System), to incorporate many navi- gation systems into a single user interface. The GPS ADS provides real-time attitude updates to a naviga- tion system such as the ECDIS. This enhances the use of radar in such a system, as there is no lag time or settling time in the attitude updates, which are com- mon in gyrocompass heading units. GPS derived atti- tude is a large contributor to an ECDIS, as it suffers no degradation at the higher latitudes, unlike a mag- netic or gyrocompass. Gyrocompass performance suf- fers at latitudes above 70” due to the magnification of imperfections. At the geographic poles the gyrocom- pass has no directive force, the driving factor for its performance. Magnetic compasses also suffer signifi- cant degradations at high latitudes due to field distur- bances. This paper describes the evolution of TRIADS tech- nology, the prototype system, system performance and test results.
Published in:	Proceedings of the 1994 National Technical Meeting of The Institute of Navigation January 24 - 26, 1994 Catamaran Resort Hotel San Diego, CA
Pages:	893 - 899
Cite this article:	Diefes, Debra L., Hazel, Geoffrey G., Greenlee, Darrell F., "Test Results of GPS Based Attitude Determining System for Marine Navigation," Proceedings of the 1994 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1994, pp. 893-899.
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