A Real-Time Short-Baseline Azimuth Determination System Using GPS

M. Vinnins and L. D.Gallop

Abstract:	Defence Research Establishment Ottawa (DREO) is performing research and development in GPS-based azimuth determination using very short antenna baseline separations. The work is based on the ongoing development of an azimuth determination capability for the Arctic sonobuoy, an in-ice Arctic surveillance sensor employed by the Canadian Armed Forces. The sonobuoy must function above a latitude of 80 degrees north with a bearing accuracy of better than 5 degrees. Due to the small diameter of the sonobuoy, the investigative work has centered on the use of extremely sho~ antenna baseline separations of 10 cm or less, as=well as the use of inexpensive, off-the- shelf GPS receivers of small size and low power consumption. Employing a software package called HEAD, developed by the Department of Geomatics Engineering at the University of Calgary, a series of tield tests was performed in the high Arctic in late 1996 using two test systems based on the Canadian Marconi CMT 8700 receiver and the Motorola VPOncore receiver designs. The results were very encouraging, resulting in the upgrading of the soflware to a real-time application, HEADRT, in preparation for the performance of a new series of tests in the summer of 1997. These results are presented in this paper. The CMT 8700 and the VPOncore were, again, the primary receiver sets evaluated and trials were conducted at DREO in Ottawa. The tests included evaluation of heading accuracy over a baseline of4 to 90 cm as well as time-to-resolution and percent availability tests performed under static conditions followed by a series of dynamic tests to evaluate the effects of foliage attenuation and ‘urban canyon’ masking. Results indicate that azimuth can be determined over the entire range of antenna separations from 4 to 90 cm but that the results become noisy and somewhat less reliable below 10 cm. At a 10 cm separation, time-to-resolution is less than 30 seconds and availability is better than 900A, with an accuracy of approximately 3 degrees under static conditions. Under dynamics, foliage attenuation resulted in some loss of performance as did masking due to large buildings in urban areas. Further performance improvements can be expected through tuning of the HEADRT algorithm and data acquisition system.
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	1763 - 1772
Cite this article:	Vinnins, M., D.Gallop, L., "A Real-Time Short-Baseline Azimuth Determination System Using GPS," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 1763-1772.
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