A method of calculating TEC with GPS data and its application to the ionospheric disturbances

The methods of calculating total electron content (TEC) by using of the dual-frequency GPS receiver are summarized in this paper. Error sources of calculating TEC using pseudorange and carrier-phase are analyzed. Considering the relation between the GPS SNR(signal-noise-rate) and elevation of the GPS satellites, the method of calculating absolute TEC by using pseudorange and carrier-phase simultaneously was particularly discussed and compared with that usually used to calculate absolute TEC by algebraic sum. The instrumental bias of satellite and receiver and their removing method are also analyzed. In order to determine the receiver bias, the GPS TEC result and the IRT model TEC result are compared. It is concluded that correcting the receiver instrumental bias using only little GPS data and IRT model is difficult, instead, statistics are necessary. With the method presented in this paper based on the above discussions, the responses for ionospheric perturbations were studied using data from four China GPS stations with emphasis on the ionospheric perturbations such as the effects of solar flare, TIDs and solar eclipse in March 9(th) 1997. The results show that the accuracy of the method is sufficient in studying the ionospheric disturbances.