Assessment of NeQuick and IRI-2016 models during different geomagnetic activities in global scale: Comparison with GPS-TEC, dSTEC, Jason-TEC and GIM

Abstract

The range delay induced by the Earth’s ionosphere is one of main errors affecting the positioning performance of Global Navigation Satellite System (GNSS). It is very significant to analyze the performance of the three-dimensional ionospheric models under different geomagnetic conditions using different methods. With the dual-frequency GPS measurements obtained from 83 globally distributed receivers of the International GNSS Service (IGS), we analyzed the performance of different three-dimensional ionospheric models, i.e. the original NeQuick2, the re-estimated NeQuickC and IRI-2016, under different ionospheric conditions. The absolute GPS-derived total electron contents (TECs), the difference of slant TEC observed in independent ground reference stations (dSTEC), the TEC derived from Jason-2 and the absolute TECs calculated from Global Ionospheric Map (GIM) are selected as reference. The validations against GPS-TEC and GIM-TEC indicate that NeQuickC can mitigate ionospheric delay by 70–76% under different geomagnetic activity levels on a global scale, which is 7–16% higher than that of NeQuick2 model, while IRI-2016 can only correct about 50% of the ionospheric delay. The validations against GPS-dSTEC presented that the NeQuickC model can make a good representation of the subtle variation in the ionospheric TEC. The validations against Jason TEC indicate that the relative error from the NeQuickC model is about 10% smaller than that from other two models over oceanic regions. The results show that the NeQuickC presents the best performance during different ionospheric activities, and the performance of those models during perturbed period is approximately 2–3 times worse than that during the quiet period.