Urban Location Simulation and Treatment of Multipath Effects

James Pautler, Timothy Orndorff and Jay Schwartz

Abstract:	A simulation has been constructed to predict expected location performance and facilitate the development of location algorithms tailored to take advantage of the non- gaussian errors encountered in the severe multipath and scattering environments of urban areas. The simulated location and digital communications system utilizes time of arrival measurements made by a network of time synchronized base station receivers to determine the position of an emitter. Data from a demonstration system agree with the statistical models implemented and are briefly described. Several location algorithms are compared including least squares and maximum likelihood methods with nominal location accuracies ranging from 10 to 100 feet under most conditions. The simulation results show one can expect at least a thirty to forty percent accuracy improvement over least squares methods when properly taking advantage of known or hypothesized error statistics. We also present a statistical quantity which is useful for predicting the accuracy of all navigation systems where signal reception is not assured, as encountered in urban areas where complete blockage of signals may occur. In addition, a related parameter is useful for analyzing the robustness of a location system to given types of component failures. The proper treatment of non-gaussian error sources has direct implications for all location systems encountering non-gaussian error sources and is illustrated by the effects of non-gaussian errors on a typical GPS receiver. Also illustrated are applications and possible solutions to Kalman filtering algorithms where conventional treatments do not adequately account for non- stationary non-gaussian error sources.
Published in:	Proceedings of the 1995 National Technical Meeting of The Institute of Navigation January 18 - 20, 1995 Disneyland Hotel Anaheim, CA
Pages:	303 - 312
Cite this article:	Pautler, James, Orndorff, Timothy, Schwartz, Jay, "Urban Location Simulation and Treatment of Multipath Effects," Proceedings of the 1995 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 1995, pp. 303-312.
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