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Remote Sens. 2018, 10(2), 169; https://doi.org/10.3390/rs10020169

The Impacts of the Ionospheric Observable and Mathematical Model on the Global Ionosphere Model

1
Institute of Space Sciences, Shandong University, 180 Wenhuaxi Road, Weihai 264209, China
2
State Key Laboratory of Geo-Information Engineering, Xi’an Research Institute of Surveying and Mapping, Xi’an 710054, China
3
Department of Land Surveying and Geo-Informatics, The Hong Kong Polytechnic University, Hong Kong 999077, China
4
Research Group of Astronomy and Geomatics (gAGE), Universitat Politecnica de Catalunya (UPC), Barcelona 08034, Spain
*
Author to whom correspondence should be addressed.
Received: 20 December 2017 / Revised: 21 January 2018 / Accepted: 22 January 2018 / Published: 25 January 2018
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Abstract

A high-accuracy Global Ionosphere Model (GIM) is significant for precise positioning and navigating with the Global Navigation Satellite System (GNSS), as well as space weather applications. To obtain a precise GIM, it is critical to take both the ionospheric observable and mathematical model into consideration. In this contribution, the undifferenced ambiguity-fixed carrier-phase ionospheric observable is first determined from a global distribution of permanent receivers. Accuracy assessment with a co-located station experiment shows that the observational errors affecting the ambiguity-fixed carrier-phase ionospheric observables range from 0.10 to 0.35 Total Electron Content Units (TECUs, where 1 TECU = 10 16 e / m 2 and corresponds to 0.162 m on the Global Positioning System, GPS L1 frequency), indicating that the ambiguity-fixed carrier-phase ionospheric observable is over one order of magnitude more accurate than the carrier-phase leveled-code one (from 1.21 to 3.77 TECUs). Second, to better model the structure of the ionosphere, a two-layer GIM has been built based on the above carrier-phase observable. Preliminary global accuracy evaluation demonstrates that the accuracy of the two-layer GIM is below 1 TECU and about 2 TECUs during low and high solar activity periods. Third, the single-frequency point positioning experiment is adopted to test the ionosphere mitigation effects of the GIMs. Positioning results demonstrate that the single-frequency positioning accuracy can be improved by more than 30% using the undifferenced ambiguity-fixed ionospheric observable-derived two-layer GIM, compared with that using the carrier-phase leveled-code ionospheric observable-based single-layer GIM. View Full-Text
Keywords: ionospheric observable; mathematical model; undifferenced ambiguity-fixed mode; two-layer ionospheric observable; mathematical model; undifferenced ambiguity-fixed mode; two-layer
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Nie, W.; Xu, T.; Rovira-Garcia, A.; Zornoza, J.M.J.; Subirana, J.S.; González-Casado, G.; Chen, W.; Xu, G. The Impacts of the Ionospheric Observable and Mathematical Model on the Global Ionosphere Model. Remote Sens. 2018, 10, 169.

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