Use of Neural Networks and Expert Systems for Rapid Differential GPS Navigation

John L. Vickery and Roger L. King

Abstract:	This work examines an intelligent DIGPS system using Neural Networks and expert systems in conjunction with utilizing the Doppler effect of the Gold Code carrier wave to build a system that quickly and accurately determines a moving users position and speed in relation to a reference point. The SIM receives data packets from the reference and the user receivers, respectively. Then, using a Neural Network, the SIM identifies the satellites that are transmitting the signals in less than one second from a cold start. Once the SIM has determined that the user and reference are receiving signals from the same satellites, it uses expert systems to determine the user position, speed and system clock error. And, if the user is moving, the SIM uses an algorithm employing the difference of the Doppler shift of the carrier wave between the user and reference to determine the user speed and position. To test the system, simulations were run at twenty distinct points on the WGS-84 globe. The simulation emulated a farm vehicle traversing rows in a hilly field traveling in a north/south direction and again in an east/west direction. Each simulation ran for one simulated hour and included corrupting the Gold Code data stream from each satellite. At no time did the system misidentify any satellite, although there were a few instances where the predictions from the ANN were low, the predictions still met the criteria for proper identification. The triangulation method yielded more accuracy than the Doppler method, but the difference was in the range of a few millimeters.
Published in:	Proceedings of the 58th Annual Meeting of The Institute of Navigation and CIGTF 21st Guidance Test Symposium (2002) June 24 - 26, 2002 Hyatt Regency Hotel Albuquerque, NM
Pages:	390 - 400
Cite this article:	Vickery, John L., King, Roger L., "Use of Neural Networks and Expert Systems for Rapid Differential GPS Navigation," Proceedings of the 58th Annual Meeting of The Institute of Navigation and CIGTF 21st Guidance Test Symposium (2002), Albuquerque, NM, June 2002, pp. 390-400.
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