Ionospheric Calibration for the Single-Frequency GPS User

Colleen H. Yinger and William A. Feess

Abstract:	This paper describes an algorithm for calibrating the Klobuchar single-frequency ionospheric model using dual-frequency measurements. The approach enables civilian users to take advantage of the emerging GPS dual-frequency civilian capability during the deployment phase by calibrating the single-frequency model using available dual-frequency measurements. The technique can also be used by an authorized user to calibrate the single-frequency ionospheric model in an unjammed environment for use in the event that one of the GPS frequencies is jammed. Analysis of real data from National Imagery and Mapping Agency (NIMA) ground stations shows that GPS user errors after correction using the standard single-frequency ionospheric model can be further reduced by 20 to 70% using a simple scale-factor and gradient calibration algorithm. Analysis of civilian user performance characterizes performance as a function of user location, solar activity, and the number of dual-frequency civilian signals. The authorized user may also benefit from singlefrequency ionospheric model calibration during periods of jamming. Performance results for authorized users are summarized as a function of time since loss of one of the frequencies. Performance can be improved by up to 70% using single-frequency model calibration rather than holding the slant ionospheric correction fixed over a onehour jamming interval.
Published in:	Proceedings of the IAIN World Congress and the 56th Annual Meeting of The Institute of Navigation (2000) June 26 - 28, 2000 The Catamaran Resort Hotel San Diego, CA
Pages:	607 - 616
Cite this article:	Yinger, Colleen H., Feess, William A., "Ionospheric Calibration for the Single-Frequency GPS User," Proceedings of the IAIN World Congress and the 56th Annual Meeting of The Institute of Navigation (2000), San Diego, CA, June 2000, pp. 607-616.
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