Evaluation of Functions for Modelling of the Effect of the Ionospheric Refraction in the Propagation of the GPS Signals

M.T. Matsuoka, P. de Oliveira Camargo

Abstract:	Nowadays, one of the main drawbacks of the GPS accuracy for L1 users is the ionospheric refraction, which affects, mainly, the point positioning. The error associated with the ionospheric refraction depends on the Total Electron Content (TEC) in the ionospheric layer, that is influenced by several variables, including the solar cycle, the season, the local time, the geographical location of the receiver and the Earth's magnetic field. The broadcast ephemeris contains information for computing the group delay, using the broadcast model. The literature reports that the model corrects 50 to 60% of the total effect of ionospheric refraction. Therefore, it is necessary a more effective strategy of eliminating the effects of the ionosphere. Some techniques and models have been developed to estimate these effects using data collected with double frequency GPS receivers. In Brazil, a regional model of the ionosphere (Mod_Ion) was developed at FCT/UNESP, which makes use of GPS data collected at the active stations of RBMC (Brazilian Network for Continuous Monitoring of GPS satellites). In this model, the ionosphere is represented analytically by a Fourier series type. In this research, others modelling functions of the ionosphere were implemented in the Mod_Ion, with objective to improve the efficiency of the model for positioning with L1 receivers. The results of the experiments showed that the functions: Fourier series, Taylor series and the polynomial, were the most effective in the correction of the systematic effect due to the ionosphere, providing an improvement in the height accuracy better than 81%.
Published in:	Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003) September 9 - 12, 2003 Oregon Convention Center Portland, OR
Pages:	1736 - 1741
Cite this article:	Matsuoka, M.T., Camargo, P. de Oliveira, "Evaluation of Functions for Modelling of the Effect of the Ionospheric Refraction in the Propagation of the GPS Signals," Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003), Portland, OR, September 2003, pp. 1736-1741.
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