基于NTCM-BC模型的全球卫星导航系统单频电离层延迟修正

选择NTCM-BC模型作为单频电离层延迟修正模型，通过非线性最小二乘拟合的方法，利用提前一天预测的电离层图（COPG文件），计算得到NTCM-BC模型修正系数；利用Klobuchar模型和IGS发布的GIM数据对NTCM-BC模型进行比较和分析.对太阳活动高、中、低年实测数据的分析结果表明:全球平均水平上，NTCM-BC模型的电离层延迟修正性能明显优于Klobuchar模型，NTCM-BC模型的TEC平均误差和均方根误差比Klobuchar模型分别下降了41%和30%；模型的TEC计算误差与太阳活动剧烈程度成正相关，即太阳活动高年模型误差较大，太阳活动低年误差相对较低.相较于磁静日，磁扰日期间Klobuchar模型和NCTM模型的误差均有一定程度的增加.此外，模型的电离层修正误差同时存在明显的纬度、季节和地方时差异. 

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.