Impact of real-time ionospheric determination on improving precise navigation with GALILEO and next-generation GPS

M.Hernández-Pajares, J.M.Juan, J.Sanz, and O.L.Colombo

Abstract:	The ionospheric differential refraction, at distances of tens of kilometers or more, is one of the main problems affecting the capability of instantaneous carrier phase ambiguity resolution. And, as a consequence, the ionosphere affects the feasibility of centimeter-accuracy navigation with dual-frequency Global Navigation Satellite Systems such as present-day GPS, as well as future systems with three frequencies, like GALILEO and the Modernized GPS. We have shown in previous work that a real-time tomographic model of the ionosphere, computed from the GPS reference network data, is accurate enough to allow GPS real-time carrier phase ambiguity resolution for a rover at hundreds of kilometers from the nearest reference site. In this work, we study the extension of such techniques to the improvement of instantaneous three-carrier phase ambiguities resolution algorithms, such as TCAR, at medium and long distances (from tens to hundreds of kilometers), and with a minimum of geodetic computation. The datasets used have been generated with a modified GNSS satellite signal generator. In particular, improvements in the instantaneous ambiguity resolution success rate with three frequencies can be attained from about 60% of all attempts in previous work to about 100% with the proposed technique, at distances of about 60 km and with low ionospheric values, and to more than 90% at distances of more than 100 km under Solar Maximum conditions.
Published in:	Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002) September 24 - 27, 2002 Oregon Convention Center Portland, OR
Pages:	2756 - 2767
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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