Passive Ranging Using the GPS

Michael H. Stockmaster, James B. Y. Tsui, Dennis M. Akos

Abstract:	Many unforeseen applications of GPS have been developed in recent years. This paper presents one such application, passive ranging using the GPS standard positioning system (GPS-SPS). A method to measure the distance between a given target and an observation point without a GPS receiver at the target or knowing the exact location of the target has been developed and tested. No signal is emitted by the user to find the distance to the target. Only the reception of GPS signals is required. This approach requires two GPS receivers. One receiver uses a conventional GPS antenna to receive the signals directly from the satellites. The second receiver uses a high gain antenna directed at the target and receives GPS signals reflected from it. The direct GPS receiver determines the positions of the satellites so the distance from the satellites to the user can be determined (and the user position if not known). The second receiver is used to process the reflected signals from the target to measure the total distance from the satellite to the target and the target to the user. Target distances of up to 64.9 meters were measured with approximately 1-2 meters of error. This paper describes the theory behind passive ranging as applied to the GPS as well as the methodology used to collect and process the GPS signals to compute the range to a given target. Experimental accuracies are given for the two demonstrations described in the paper as well as factors impacting the measurement accuracy.
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:	915 - 921
Cite this article:	Stockmaster, Michael H., Tsui, James B. Y., Akos, Dennis M., "Passive Ranging Using the 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. 915-921.
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