Regional Ionospheric TEC Modeling and Accuracy Analysis Based on Observations from a Station

  Objectives  Establishing a regional ionospheric total electron content (TEC) model from a single station is much more efficient than developing a global multistation model because of its small amount of data. However, the single-station regional ionospheric TEC model has a scope of application. Therefore, the study of the scope and accuracy of a single-station regional ionospheric TEC model can effectively provide high-precision ionospheric delay correction for single-frequency users in the region.

  Methods  With 2-to 15-order spherical harmonic functions, single-station regional ionospheric TEC models are established using global navigation satellite systems (GNSS) observations from 16 stations in the European region during day of year (DOY) 357—363 in 2017, a period of calm solar activity and without a magnetic storm. The average ionospheric TEC values and average root mean square (RMS) values at all grid points in the longitude–latitude ranges of 0°×0°, 10°×5°, 10°×10°, 10°×15°, 20°×15°, and 20°×20° are compared with those of global ionospheric products such as Center for Orbit Determination in Europe (CODE), International GNSS Monitoring and Assessment System (iGMAS), and International GNSS Service (IGS) for the determination of the scope of application and accuracy of the single-station regional ionospheric TEC models.

  Results  (1) The 16 single-station regional ionospheric TEC models based on 2-to-15-order spherical harmonic functions have the average TEC values within the value range of CODE, iGMAS, and IGS in different regions. In other words, within the latitude-longitude range of 20°×20°, the TEC values of the single-station regional ionospheric models established by the proposed method are comparable to those of CODE, iGMAS, and IGS. (2) The RMS values of regional ionospheric TEC models established with the data of 16 single stations and 2-to-15-order spherical harmonic functions are different from those of IGS beyond the latitude-longitude range of 10°×10°. The lower order of spherical harmonic functions in the latitude‍-longitude range of 10°×10° corresponds to smaller RMS values of the models. The accuracy of the single-station regional ionospheric TEC models based on low-order (2×2 or 3×3) spherical harmonic functions is similar to that of IGS in the 10°×10° range centered on a single station, namely that the applicable radius of the single-station regional ionospheric TEC models is about 600 km and the accuracy is about 1 TECU. (3) The single-station regional ionospheric TEC models are highly consistent with the IGS global ionospheric TEC model, which indicates that the accuracy of the single-station regional ionospheric TEC models based on low-order (2×2 or 3×3) spherical harmonic functions is comparable to that of the IGS global ionospheric TEC model.

  Conclusions  The results show that the single-station regional ionospheric TEC models based on low-order (2×2 or 3×3) spherical harmonic functions has the comparable accuracy to that of global ionospheric products such as CODE, iGMAS, and IGS, which is about 1.0 TECU, within the latitude‐longitude range of 10°×10° (radius < 600 km) centered on a single station. Thus, the global ionospheric TEC model can be replaced by the ionospheric TEC model established with data of a single station in a certain region (radius less than 600 km), with which the high-precision ionospheric delay correction can be efficiently provided for single-frequency users in the region.