Real-Time WADGPS Ionospheric Correction Filter

Tysen Mueller and Paul Davis

Abstract:	Seagull has designed and developed a real-time Wide Area DGPS (WADGPS) software code which estimates the ionospheric delay corrections for a Continental US (CONUS) user grid map, based on dual-frequency receiver measurements. This software was developed for Satloc Precision GPS Applications, as interim software, for the L-Band WADGPS network. A Kalman filter is used to estimate the spatially-distributed scale factors to a nominal ionospheric delay model (currently the GPS Broadcast Ionosphere Model) using the dual-frequency measurements. The scale factors are represented as a set of two-dimensional Fourier series coefficients in a sun-fixed reference frame. To assure good fits of the measurement data to the earth-fixed user grid map in data-sparse regions, the scale factor estimation error sigmas are mapped into ionospheric vertical grid sigmas. If these grid sigmas exceed a specified level, the local (2 deg. x 2 deg.) grid map estimates default to the model estimates. The results from tests with both the simulated and field data indicate sub-meter accuracy is achieved with this software.
Published in:	Proceedings of the 1998 National Technical Meeting of The Institute of Navigation January 21 - 23, 1998 Westin Long Beach Hotel Long Beach, CA
Pages:	753 - 761
Cite this article:	Mueller, Tysen, Davis, Paul, "Real-Time WADGPS Ionospheric Correction Filter," Proceedings of the 1998 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 1998, pp. 753-761.
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