Construction of Ionospheric TEC Assimilation Model Based on Chapman Function

The TEC (total electron content) of ionosphere is one of the major error resources for the accuracy of satellite navigation positioning. To construct a precise ionospheric model, a background field for an ionospheric TEC assimilation model, which is on basis of physical mechanism, was constructed based on the Chapman function. Residual and relative accuracy analyses of model were based on the IGS (international GNSS service) TEC data sample (low latitude, mid-latitude and high latitude within four periods of time, 2008), when the ionosphere IGS TEC value for sparse points were known and assimilated. Also, 2h short-term prediction and one day predictions are presented. The one-day prediction results were compared with the IGS TEC. The results showed that: 1) 92% of TEC calculation residuals in the assimilation model were less than ±2 TECU, while the relative accuracy of TEC computed by the proposed model was above 90% in addition to the edge of the areas; 2) the percentage of 2h short-term and 1 day predicted residuals, less than ±3 TECU, were 81.8% and 81.5%, respectively.