GPS Ionosphere Determination Using L1 Only

Paul Nisner, Mike Trethewey

Abstract:	Knowledge of signal delays caused by the ionosphere is important in wide area augmentation systems such as WAAS and EGNOS. A dual frequency receiver can identify and correct for errors introduced by the ionosphere but currently neither GPS or GLONASS offer ICAO the second frequency for civil use. The single frequency method for ionosphere determination has the benefit that it is not reliant on the military controlled L2 signals. Whilst the theory exploited in this method has a solid foundation, in practice difficulties are experienced with multi-path reception and in determining carrier phase cycle ambiguities. A Kalman filter based algorithm is presented that integrates measurements from all satellites in view with a regional ionosphere model. Results are presented from data collection over an extended period that encompasses seasonal changes from a number of sites widely distributed. These sites include both mid-latitude and equatorial regions. Varying degrees of multi-path reception was experienced and these effects are demonstrated in the results data. Comparison is made with the GPS Klobuchar model and the standard dual frequency GPS approach. This comparison demonstrates the accuracy of the technique, its potential within augmentation systems, and its robustness under a wide range of conditions and signal characteristics.
Published in:	Proceedings of the 1996 National Technical Meeting of The Institute of Navigation January 22 - 24, 1996 Loews Santa Monica Hotel Santa Monica, CA
Pages:	625 - 635
Cite this article:	Nisner, Paul, Trethewey, Mike, "GPS Ionosphere Determination Using L1 Only," Proceedings of the 1996 National Technical Meeting of The Institute of Navigation, Santa Monica, CA, January 1996, pp. 625-635.
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