Effectiveness of Two Satellite Tracking in Urban Canyon Environments

J. Blake Bullock, G. Jeffrey Geier, T. Michael King, and Howard L. Kennedy

Abstract:	Urban canyon environments can cause severe GPS satellite blockage which reduces the coverage area of GPS. Low cost GPS receivers make use of fast reacquisition strategies and parallel channel tracking to minimize the effects of blockage and improve the coverage and accuracy in these areas. A two dimensional position fix traditionally requires observations to three satellites to solve for the horizontal position and the receiver clock offset. If the receiver clock offset is treated as a known parameter, then only two satellite observations are required to solve for a two dimensional position. This would improve the coverage in urban canyon environments while sacrificing accuracy due to the instability of the receiver oscillator. This paper investigates the gain in coverage and the reduction of accuracy when two satellites are used for a position solution. Data collected in an urban canyon environment is used to analyze typical geometries when only two satellites are available. The effect of various drift rates in oscillators is also taken into consideration. Finally, two satellite tracking is compared with other methods of extending GPS coverage in urban canyons.
Published in:	Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996) September 17 - 20, 1996 Kansas City, MO
Pages:	1699 - 1707
Cite this article:	Bullock, J. Blake, Geier, G. Jeffrey, King, T. Michael, Kennedy, Howard L., "Effectiveness of Two Satellite Tracking in Urban Canyon Environments," Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996), Kansas City, MO, September 1996, pp. 1699-1707.
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