Estimation of Ionospheric Total Electron Content From a Multi-GNSS Station in China

Ionospheric total electron content (TEC) is an important parameter in ionospheric researches and applications. However, the determination of the absolute value of TEC can be greatly influenced by the differential code biases (DCBs) estimation. Nowadays, there are more and more Global Navigation Satellite System (GNSS) signals available all over the world, which allow us to solve TEC and DCBs with the hypothesis of local spherical symmetry (LSS) imposed on the dual-frequency observations from only one individual station. For comparison, the results based on the global ionospheric map (GIM) act as a reference in this article. On the one hand, different combinations of Global Positioning System (GPS), GLONASS, and BeiDou Navigation Satellite System (BDS) are considered to illustrate the significance of multi-GNSS observations, with the mixed GPS, GLONASS, and BDS combination performing best when compared to the referenced results. On the other hand, different parameters in LSS condition are taken into account to investigate the suitable geometric constraint of LSS, with the differential longitude, latitude, and epoch suggested to be 3.0°, 0.6°, and 4 min, respectively. Moreover, a group of detailed comparisons from several different stations also show that the combined DCBs and ionospheric TEC derived from our method are compatible with those from the GIM-aided method, especially in the low-latitude area. In summary, with the advantage of the multi-GNSS signals from an individual station, our method can estimate the ionospheric TEC and DCBs independently, which could provide a potential tool in the future real-time applications.