Modelling of GAGAN TEC data using Spherical Harmonic Functions

Satellite based augmentation system (SBAS) in Indian region is known as GPS aided geo augmented navigation system (GAGAN). As India comes under low latitude region, more care has to be taken to characterize the ionosphere due to equatorial anomaly conditions and large irregularities and develop appropriate ionospheric delay model for GAGAN. An ionospheric model based on spherical harmonic function (SHF) is considered in this paper. 12 GAGAN TEC stations data is used. The results of the SHF model are presented in terms of accuracy of the residuals between measured and estimated TECs. Preliminary results are encouraging and consistent. Further investigations are under progress.