Assessment of International GNSS Service Global Ionosphere Map products over China region based on measurements from the Crustal Movement Observation Network of China

The global ionosphere maps (GIM) provided by the International GNSS Service (IGS) are extensively utilized for ionospheric morphology monitoring, scientific research, and practical application. Assessing the credibility of GIM products in data-sparse regions is of paramount importance. In this study, measurements from the Crustal Movement Observation Network of China (CMONOC) are leveraged to evaluate the suitability of IGS-GIM products over China region in 2013–2014. The indices of mean error (ME), root mean square error (RMSE), and normalized RMSE (NRMSE) are then utilized to quantify the accuracy of IGS-GIM products. Results revealed distinct local time and latitudinal dependencies in IGS-GIM errors, with substantially high errors at nighttime (NRMSE: 39%) and above 40° latitude (NRMSE: 49%). Seasonal differences also emerged, with larger equinoctial deviations (NRMSE: 33.5%) compared with summer (20%). A preliminary analysis implied that the irregular assimilation of sparse IGS observations, compounded by China’s distinct geomagnetic topology, may manifest as error variations. These results suggest that modeling based solely on IGS-GIM observations engenders inadequate representations across China and that a thorough examination would proffer the necessary foundation for advancing regional total electron content (TEC) constructions.