Precise Ionospheric Determination and its Application to Real-Time GPS Ambiguity Resolution

M. Hemtindez-Pajares, J. M. Juan, J. Sanz, O.L. Colombo

Abstract:	The influence of the ionosphere is one of the main prob-lems in the real-time ambiguity resolution for the carrier phase GPS data in radionavigation, especirdly with high geomag-netic activity or close to the next Solar Maximum at year 2000. Therefore, it is important to have a precise estimation of the ionospheric delays. In the first part of this paper we present a comparison at real-time mode, and using only the carrier phase, of the tomo-graphic model with the traditionrd 1 fixed height layer model, and it is shown the reduction of the error of the absolute, sin-gle difference and double d~fferenced ionospheric corrections. Quiet geomagnetic conditions are simulated with the Intern-ational Reference Ionosphere model, with real geometry for network of stations at distances of 400-1000 km in North-America. In the second part we perform an assessment of the pro-posed real-time tomographic model, feed with real carrier pha-se data only, and in three situations with different geomag-netic activity. In the moderate and h@ activity scenarios, the resolution of the widelane double difference ambiguities is successful for the greatest part of cases (95Y0 for elevations greater than 20 degrees) when the tomographic ionospheric correction is included. In the storm scenario (Kpm 8), the re-sults are poorest (60%) at times with highest electron content variations (5 TECU in 2 minutes), but they are better than in case of neglecting the double difference ionospheric cor-rection.
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:	1409 - 1418
Cite this article:	Hemtindez-Pajares, M., Juan, J. M., Sanz, J., Colombo, O.L., "Precise Ionospheric Determination and its Application to Real-Time GPS Ambiguity Resolution," Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999), Nashville, TN, September 1999, pp. 1409-1418.
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