Real-Time Ambiguity-fixed Precise Point Positioning Using Global and Regional Reference Networks
Committee MemberEl-Sheimy, Naser
ClassificationGlobal Navigation Satellite System (GNSS)
Orbit arc length
Fractional Cycle Bias (FCB)
PPP Ambiguity Resolution (AR)
Regional augmented PPP
Atmospheric stochastic model
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AbstractAmbiguity resolution with PPP is able to reduce the long convergence time. However, real-time PPP suffers from slow ambiguity-fixing due to the real-time orbits and clocks with lower quality. The research in this thesis aims at addressing several challenging issues of PPP ambiguity resolution in real-time situations. The determination of real-time orbits and clocks has first been investigated in this thesis. The real-time orbits have been generated based on the estimated initial parameters with previous data, while the real-time satellite clocks and Fractional Cycle Biases (FCBs) have been estimated from a network of GNSS data. Then a software package has been developed to generate the real-time orbits and clocks as well as FCBs for assessing the performance of PPP ambiguity resolution and positioning. The Solar Radiation Pressure (SRP) parameters have been identified as the key factor driving orbit prediction accuracies as a function of arc length. Based on the minimization of SRP parameter variation, the optimal arc length has been determined for precise orbit prediction, with which the high-accuracy satellite clocks can be estimated. In addition, PPP ambiguity resolution performance has been quantitatively evaluated using the real-time orbits and estimated clocks with different arc lengths. A cascaded method of satellite FCB estimation has been developed to improve real-time PPP ambiguity resolution. The satellite clocks have been first estimated to compensate part of real-time orbit errors. Then the Narrow-Lane (NL) FCBs have been subsequently estimated as one directional-independent term and three direction-dependent terms, rather than a directional-independent term as did in the past. The improvements of the resulting ambiguity fix rates and positioning accuracy have been demonstrated. A new method for regional augmented PPP by using atmospheric corrections and their stochastic model derived from regional reference networks has been developed. The interpolated atmospheric corrections have been then applied by users as the pseudo-observations with the estimated stochastic model to properly describe their uncertainties. Some future work has been provided in the end to consider satellite FCB estimation and PPP ambiguity resolution, validation of Cascaded Orbit Error Separation (COES) method with multi-constellation data, and improvement of the integer ambiguity resolution in real-time PPP.
CitationLi, Y. (2016). Real-Time Ambiguity-fixed Precise Point Positioning Using Global and Regional Reference Networks (Unpublished doctoral thesis). University of Calgary, Calgary, AB. doi:10.11575/PRISM/27543
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