Issues in Ambiguity Resolution for Precise Point Positioning

Paul Collins and Sunil Bisnath

Abstract:	Ambiguity Resolution for Precise Point Positioning (PPP) is possible when the system hardware delays have been properly accounted for in the observation model. Even when the carrier phase ambiguity parameters are formally integer in nature however, there is still a substantial convergence period required before meaningful ambiguity resolution is possible. During the convergence period, the parameters of interest are also converging and so the impact of integer fixing is generally limited to small improvements for long-period static positioning. It remains a challenge therefore to use PPP in a real-time scenario requiring rapid cm-level positioning. Recent research has shown the utility of explicitly accounting for the ionospheric delay instead of eliminating it with linear combinations of observations. We show here how this brings PPP more in-line with the Real-Time Kinematic (RTK) technique and how ambiguity resolution in both techniques is substantially influenced by the ionosphere. An expanded observation model can permit explicit estimation of ionospheric delays that can be constrained to permit instantaneous re-initialisation of the PPP solution under some circumstances. Where this is not possible seems to be largely due to the influence of the pseudorange measurement noise and multipath.
Published in:	Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011) September 20 - 23, 2011 Oregon Convention Center, Portland, Oregon Portland, OR
Pages:	679 - 687
Cite this article:	Collins, Paul, Bisnath, Sunil, "Issues in Ambiguity Resolution for Precise Point Positioning," Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011), Portland, OR, September 2011, pp. 679-687.
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