| Abstrakt: |
The ionosphere is a crucial factor affecting Global Navigation Satellite System positioning. The Global Ionosphere Map (GIM) or the International Reference Ionosphere (IRI) model can be used for regional ionospheric correction. Since southern China is located near the electron density equatorial anomaly, this study evaluates the performance of the Wuhan University GIM (WHU‐GIM) and the IRI‐2020 from 2008 to 2020 over the China region. The comparison indicates that the Total Electron Content (TEC) from IRI‐2020 is lower than that from WHU‐GIM overall, the discrepancy is more obvious in high solar conditions and low‐latitude regions. The differential Slant TEC (dSTEC) during a phase‐arc with about 0.1 TECU accuracy derived from Global Positioning System (GPS) observations is used for model validation, the results show that the accuracies of WHU‐GIM and IRI‐2020 are 3.14 and 4.57 TECU, respectively. The dSTEC error is larger at low latitudes and decreases with increasing latitude. GPS‐derived TEC is taken for reference to evaluate the model reliability. Results show that both models can reproduce the diurnal TEC variations, but IRI‐2020 is more influenced by geomagnetic activities. The TEC correction percentage for IRI‐2020 is about 60%–80% under different ionospheric conditions, while for WHU‐GIM is 80%–90%. The Single‐Frequency Precise Point Positioning is performed with the ionosphere delay corrected by the two models, respectively. The positioning errors show that using IRI‐2020 has a lower accuracy, and the TEC discrepancy of the IRI‐2020 can cause a large bias in the up direction, especially at low‐latitude regions. Plain Language Summary: The ionosphere is a part of the Earth's atmosphere within an altitude of 60–1,000 km from the ground. The ionized molecules and free electrons that exist in the ionosphere will affect the Global Navigation Satellite System signals, and reduce the positioning accuracy finally. Ionospheric models such as the Global Ionospheric Map (GIM) and the International Reference Ionosphere (IRI) model provide the Total Electron Content (TEC) which is always used to mitigate ionospheric errors. The China region is close to the equator where the ionosphere is more active and disturbed, and is important to assess the performance of these two models in this area. This study evaluates the Wuhan University GIM (WHU‐GIM) and the IRI‐2020 model for 13 years according to the differential Slant TEC data, Global Positioning System TEC and Single‐Frequency Precise Point Positioning (SF‐PPP) technique. The results indicate that the TEC from the IRI‐2020 model is lower than that from the WHU‐GIM, especially under high solar conditions and in low‐latitude regions. According to the result of the SF‐PPP, the accuracy of the IRI‐2020 model is worse than WHU‐GIM, and the low TEC of the IRI‐2020 could cause a large bias in the up direction at the low‐latitude regions over China. Key Points: An assessment of Wuhan University Global Ionosphere Map (WHU‐GIM) and International Reference Ionosphere (IRI)‐2020 was conducted from 2008 to 2020 over the China region, with an overall better performance of WHU‐GIMCompared to WHU‐GIM, the Total Electron Content (TEC) derived from IRI‐2020 model is lower, such discrepancies are more obvious under the high solar conditionIRI‐2020 can be more influenced by geomagnetic storms, and its low TEC is reflected in a larger bias in the up component resulting from Single‐Frequency Precise Point Positioning [ABSTRACT FROM AUTHOR] |
