Improving Ionospheric Estimation in the Quasi-Ionosphere-Free Ambiguity Resolution Strategy

N. Brown

Abstract:	In order to resolve the integer ambiguities over long GPS baselines, the residual ionospheric error remaining after double differencing must be modeled. To resolve the L1 and L2 integer ambiguities directly this means that the ionospheric error must be estimated for every satellite, every epoch. The resulting number of parameters is usually too large to be dealt with using conventional estimation techniques, such as least squares. Currently the technique of pre-elimination is used to overcome this problem. One drawback of the pre-elimination technique is that it is less effective when the ionospheric parameters are dominated by systematic error, such as is the case with long (>500km) baselines. Current deterministic models of the ionosphere are not able to entirely address this limitation. Additionally, pre-elimination makes modelling the stochastic behavior of the ionosphere (such as temporal correlation) difficult. This paper proposes an alternative technique for estimating the ionospheric path delays based on the theory of sequential phased adjustments.
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:	2637 - 2648
Cite this article:	Brown, N., "Improving Ionospheric Estimation in the Quasi-Ionosphere-Free Ambiguity Resolution Strategy," 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. 2637-2648.
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