Ionospheric Delay Correction of Single-frequency for Global Navigation Satellite System Based on NTCM-BC Model

Ionospheric delay is one of dominant factors that affect single-frequency positioning accuracy of Global Navigation Satellite System (GNSS). It is very important for GNSS single-frequency users to study the ionospheric delay correction model of high accuracy. In this paper, an ionospheric correction algorithm called Neustrelitz TEC Broadcast model (NTCM-BC) is chosen as the single-frequency ionospheric delay correction model. The correction coefficients of NTCM-BC model are obtained by non-linear least square fitting method based on the 1-day predicted ionospheric maps (COPG file). The results of NTCM-BC model have been compared with Klobuchar model and IGSG's Global Ionosphere Maps (GIM). It can be concluded that, for solar maximum, moderate or minimum, NTCM-BC model can achieve a significantly better performance than Klobuchar model in global average. The mean error and Root Mean Square Error (RMSE) of TEC calculation decrease by 41% and 30%, respectively. The TEC deviations of the two models have positive correlations with solar activity. Compared with the geomagnetic quiet days, the errors of Klobuchar and NTCM-BC models will increase during the geomagnetic perturbed days. Moreover, the correction error depends on latitude, season and local time.