Comparison of 4D tomographic mapping versus thin-shell approximation for ionospheric delay corrections for single-frequency GPS receivers over North America |
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Authors: | Damien J Allain Cathryn N Mitchell |
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Institution: | (1) Department of Electronic and Electrical Engineering, University of Bath, Bath, BA2 7AY, UK |
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Abstract: | The majority of navigation satellite receivers operate on a single frequency. They compensate for the ionospheric delay using
either an ionospheric model which typically only corrects for 50% of the delay or a thin-shell map of the ionosphere. A 4D
tomographic imaging technique is used to map the free electron density over the full-height of the ionosphere above North
America during autumn 2003. The navigation solutions computed using correction based upon the thin-shell and the full-height
maps are compared in this paper. The maps are used to calculate the excess propagation delay on the L1 frequency experienced
by GPS receivers at selected locations across North America. The excess delay is applied to correct the single-frequency pseudorange
observations at each location, and the improvements to the resulting positioning are calculated. It is shown that the thin-shell
and full-height maps perform almost as well as a dual-frequency carrier-smoothed benchmark and for most receivers better than
the unfiltered dual-frequency benchmark. The full-height corrections perform well and are considerably better than thin-shell
corrections under extreme storm conditions. |
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