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IGS real-time service for global ionospheric total electron content modeling

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Benefiting from global multi-frequency and multi-constellation GNSS measurements provided by the experimental International GNSS real-time service (IGS RTS), a predicting-plus-modeling approach employed by Chinese Academy of Sciences (CAS) for the routine generation of real-time global ionospheric maps (RT-GIM) is first reported. Along with RT-GIMs generated by Universitat Politècnica de Catalunya (UPC), the quality of CAS and UPC RT-GIMs in IONEX format is assessed during a low soar activity period from September 2017 to December 2019. The differential slant total electron contents (dSTEC) derived from 50 GPS stations of the IGS and Jason-3 vertical TECs (VTEC) over the ocean are used as references. In comparison with different reference TECs, CAS and UPC RT-GIMs are approximately 1.7–4.9% and 8.6–12.5% worse than the respective post-processed GIMs CASG and UQRG, respectively. Using RTCM ionospheric data streams from CAS, Centre National d’Etudes Spatiales (CNES) and UPC, the first experimental IGS combined RT-GIM is generated and validated in actual real-time conditions. Compared to Jason-3 VTEC measurements available during the period of common availability, from October 2018 to April 2019, RT-GIM discrepancies present similar relative RMS errors, which are 33, 36, 36 and 38% for CNES, combined one, UPC and CAS, respectively. Aside from a better understanding of the influence of working in the original IONEX versus RTCM ionospheric formats, the update to a new experimental adaptation of RT strategy is highlighted by UPC, and the computation of multi-layer RT-GIM is emphasized by CAS in view of the inadequacy of single-layer ionospheric assumption in the presence of large latitudinal gradients.

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Data availability

CAS, CNES and UPC RT ionospheric data streams are routinely transmitted via the respective NTRIP caster. CAS RT-GIMs in IONEX format are publicly available from


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The authors acknowledge the IGS and other agencies for providing real-time GNSS data and products. This work was supported by the Strategic Priority Research Program of Chinese Academy of Sciences (XDA17010202), the National Natural Science Foundation of China (41674043, 41704038), the National Key Research Program of China (2017YFGH002206), and the Youth Innovation Promotion Association of the Chinese Academy of Sciences.

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ZL, NW and MH designed the research; ZL and NW performed the research and wrote the paper; ZL, NW, MH analyzed the data; AL, JZ AG and DR also contributed to the data analysis; YY, AK, HY, DL and AB gave helpful discussions on additional analyses and result interpretation.

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Correspondence to Zishen Li.

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Li, Z., Wang, N., Hernández-Pajares, M. et al. IGS real-time service for global ionospheric total electron content modeling. J Geod 94, 32 (2020).

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