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Open AccessArticle

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.
Remote Sens. 2018, 10(2), 169; https://doi.org/10.3390/rs10020169
Received: 20 December 2017 / Revised: 21 January 2018 / Accepted: 22 January 2018 / Published: 25 January 2018
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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MDPI and ACS Style

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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