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<p>Traditional broadcast ionospheric models depend on real-time updates of broadcast parameters from the GNSS broadcast ephemeris data message (BRDM), which may become unavailable when broadcast parameters are absent in the transmitted messages. To address this limitation, this study introduces two modified broadcast ionospheric models, MNTCM-SHC0 and MNTCM-GEC, based on the Neustrelitz TEC Model (NTCM). These modified models require only a single broadcast parameter—either the spherical harmonic coefficient of degree 0 (SHC0) or the global electron content (GEC). This design ensures reliable ionospheric corrections when ionospheric broadcast parameters cannot be effectively retrieved from the BRDM file by utilizing publicly available GEC or SHC0 data from the previous day's International GNSS Service (IGS) products. While maintaining theoretical equivalence, the MNTCM-GEC model benefits from a wider range of data sources generated through diverse methods, thereby enhancing its robustness. In contrast, the MNTCM-SHC0 model is distinguished by its computational simplicity and operational efficiency. Comparisons with the IGS final combined global ionospheric maps (GIMs) indicate that the root mean square error (RMS) for the MNTCM-SHC0, MNTCM-GEC, NTCM-GlAzpar (NTCM-G), and NeQuickG models during the low solar activity year of 2020 are 2.44, 2.46, 2.81, and 4.04 TECU, respectively. During the high solar activity year of 2023, the corresponding RMS values are 7.97, 8.03, 8.36, and 9.47 TECU, respectively. Comparisons with Jason-3 altimeter datasets reveal that MNTCM-SHC0 and MNTCM-GEC perform better than NTCM-G and NeQuickG, with mean standard deviations (STD) of residuals of 6.68, 6.64, 6.92, and 7.18 TECU, respectively. Experimental results from standard point positioning (SPP) indicate that the 95th percentiles of the 3D positioning errors using the MNTCM-SHC0, MNTCM-GEC, NTCM-G, and NeQuickG models are 3.11&#xa0;m, 3.12&#xa0;m, 3.19&#xa0;m, and 3.65&#xa0;m for 2020, and 6.82&#xa0;m, 6.81&#xa0;m, 6.86&#xa0;m, and 6.90&#xa0;m for 2023, respectively. The RMS of the differences between MNTCM-SHC0 model estimates using TEC data from 2013 to 2017 and 2010 to 2022 are less than 0.06 TECU, indicating that the temporal range of historical TEC observational data has a negligible impact on model performance.</p>

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Modified NTCM models driven by the mean of global ionospheric total electron content (TEC): MNTCM-SHC0 and MNTCM-GEC

  • 期刊论文

  • 发表日期：

    2025年6月5日

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  • Hanying Xu,
  • Min Li,
  • Yunbin Yuan,
  • Ting Zhang,
  • Xingliang Huo,
  • Wenyao Zhang

摘要

Traditional broadcast ionospheric models depend on real-time updates of broadcast parameters from the GNSS broadcast ephemeris data message (BRDM), which may become unavailable when broadcast parameters are absent in the transmitted messages. To address this limitation, this study introduces two modified broadcast ionospheric models, MNTCM-SHC0 and MNTCM-GEC, based on the Neustrelitz TEC Model (NTCM). These modified models require only a single broadcast parameter—either the spherical harmonic coefficient of degree 0 (SHC0) or the global electron content (GEC). This design ensures reliable ionospheric corrections when ionospheric broadcast parameters cannot be effectively retrieved from the BRDM file by utilizing publicly available GEC or SHC0 data from the previous day's International GNSS Service (IGS) products. While maintaining theoretical equivalence, the MNTCM-GEC model benefits from a wider range of data sources generated through diverse methods, thereby enhancing its robustness. In contrast, the MNTCM-SHC0 model is distinguished by its computational simplicity and operational efficiency. Comparisons with the IGS final combined global ionospheric maps (GIMs) indicate that the root mean square error (RMS) for the MNTCM-SHC0, MNTCM-GEC, NTCM-GlAzpar (NTCM-G), and NeQuickG models during the low solar activity year of 2020 are 2.44, 2.46, 2.81, and 4.04 TECU, respectively. During the high solar activity year of 2023, the corresponding RMS values are 7.97, 8.03, 8.36, and 9.47 TECU, respectively. Comparisons with Jason-3 altimeter datasets reveal that MNTCM-SHC0 and MNTCM-GEC perform better than NTCM-G and NeQuickG, with mean standard deviations (STD) of residuals of 6.68, 6.64, 6.92, and 7.18 TECU, respectively. Experimental results from standard point positioning (SPP) indicate that the 95th percentiles of the 3D positioning errors using the MNTCM-SHC0, MNTCM-GEC, NTCM-G, and NeQuickG models are 3.11 m, 3.12 m, 3.19 m, and 3.65 m for 2020, and 6.82 m, 6.81 m, 6.86 m, and 6.90 m for 2023, respectively. The RMS of the differences between MNTCM-SHC0 model estimates using TEC data from 2013 to 2017 and 2010 to 2022 are less than 0.06 TECU, indicating that the temporal range of historical TEC observational data has a negligible impact on model performance.