A New Ionospheric Model for Wide Area Differential GPS: The Multiple Shell Approach

A. Komjathy, B.D. Wilson, T.F. Runge, B.M. Boulat, A.J. Mannucci, L. Sparks and M.J. Reyes

Abstract:	Global Ionospheric Modeling (GIM) algorithms have been recently enhanced to solve for electron content distributions on multiple horizontal grids distributed vertically (multiple shells), instead of using a single grid at a fixed height (single shell). We are assessing this new ionospheric model for application in Wide Area Differential GPS (WADGPS) systems over the coterminous United States (CONUS). The additional parameters from multiple vertical shells allow GIM to better model the height variation of ionospheric electron density along the GPS raypaths, and accommodate significant diurnal height variations of the ionosphere that are ignored in a fixed-height single shell approach. This new model is conceptually a simple extension of several existing WADGPS algorithms and may offer benefits similar to various forms of ionospheric tomography. We compare solutions that model the ionosphere as a correlated random-walk stochastic process (the standard GIM approach) using multiple shells, with an older strategy assuming the ionospheric centroid height to be fixed. It is shown that the multishell approach improves slant ionospheric delay accuracy at low elevation angles by about 0.2 meter RMS on L1 and reduces systematic error in the GPS inter-frequency bias estimates by a factor of 2−4.
Published in:	Proceedings of the 2002 National Technical Meeting of The Institute of Navigation January 28 - 30, 2002 The Catamaran Resort Hotel San Diego, CA
Pages:	460 - 466
Cite this article:	Komjathy, A., Wilson, B.D., Runge, T.F., Boulat, B.M., Mannucci, A.J., Sparks, L., Reyes, M.J., "A New Ionospheric Model for Wide Area Differential GPS: The Multiple Shell Approach," Proceedings of the 2002 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2002, pp. 460-466.
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