Resolving Carrier-Phase Ambiguities On The Fly, At More Than 100 km From Nearest Reference Site, With The Help Of Ionospheric Tomography

Oscar L. Colombo, Manuel Hernández-Pajares, J. Miguel Juan, Jaume Sanz, Julia Talaya

Abstract:	In this paper we address the question of how to resolve GPS carrier phase ambiguities precisely and quickly, when the rover is more than 100 kilometers from the nearest reference site, in order to obtain sub-decimeter (r.m.s.) position in real-time (and, by implication, in post-processing). To do this reliably, ionospheric refraction has to be corrected very accurately. For distances of up to a few hundred kilometers, dual-frequency GPS data from permanent control stations may be used to obtain the necessary ionospheric refraction information. The ionosphere over the area served by the stations has to be mapped using their carrier phase data, also in real-time, by computed ionospheric tomography. The resulting map is used to produce information that is transmitted to the user, along with range and time corrections. The user can then calculate very precise corrections for ionospheric refraction at the location of the roving receiver. After a successful preliminary test using 1997 data from the core control stations of the CATNET network in Catalunya, (Catalonia) Spain, a second test involving those, as well as a road vehicle, was conducted in March of 1999, at a distance of 116 km from the nearest reference station. The data were processed after the test, but simulating a real-time analysis. As reported here, repeated attempts at resolving all the L1 and L2 ambiguities proved successful over a total period of two hours.
Published in:	Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999) September 14 - 17, 1999 Nashville, TN
Pages:	1635 - 1642
Cite this article:	Colombo, Oscar L., Hernández-Pajares, Manuel, Juan, J. Miguel, Sanz, Jaume, Talaya, Julia, "Resolving Carrier-Phase Ambiguities On The Fly, At More Than 100 km From Nearest Reference Site, With The Help Of Ionospheric Tomography," Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999), Nashville, TN, September 1999, pp. 1635-1642.
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