Augmentation of GPS/GLONASS For Vehicular Navigation Under Signal Masking

G. Lachapelle, S. Ryan, M. Petovello and J. Stephen

Abstract:	In urban canyons and under tree-lined streets, the line-of-sight GPS signals are masked by obstructions, resulting in degraded geometry and accuracy or unavailability. In the case of straight streets, the problem is particularly significant in the across-track direction. In the case of curved streets, the problem is acute in all directions. The use of combined GPS/GLONASS results in an increase of about twice the number of satellites available above the horizon. A series of simulations and field trials were conducted under various GPS and GPS/GLONASS constellations under various types of isotropic and anisotropic signal masking situations. Ashtech GG24TM GPS/GLONASS receivers operating in differential mode were used for the trials. A comparison of GPS versus GPS/GLONASS results shows an increase in availability of 10% to 40%, depending on the mask angle used. Augmentation of GPS and GPS/GLONASS with height and precise clock constraints results in a further improvement, the magnitude of which is again a function of the mask angle. In urban canyons with mask angles of 70*or higher, availability of any of the above combinations remains very low however, demonstrating the need for additional sensor aiding.
Published in:	Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997) September 16 - 19, 1997 Kansas City, MO
Pages:	1511 - 1519
Cite this article:	Lachapelle, G., Ryan, S., Petovello, M., Stephen, J., "Augmentation of GPS/GLONASS For Vehicular Navigation Under Signal Masking," Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997), Kansas City, MO, September 1997, pp. 1511-1519.
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