Modelling of ionospheric time delay of Global Positioning System (GPS) signals using Taylor series expansion for GPS Aided Geo Augmented Navigation applications

The positional accuracy of Indian Global Positioning System Aided Geo Augmented Navigation (GAGAN) system is affected by many errors and among them the ionospheric time delay error is the predominant error. The Indian ionosphere is characterised by large gradients, intense irregularities and equatorial anomaly conditions and hence suitable ionospheric model is necessary for GAGAN. Compared with global and regional ionospheric models, not much significant work is reported on local ionospheric models for Indian region. In this study, using Indian Satellite Based Augmentation System data, a local ionospheric model based on Taylor series expansion (TSE) is used. Initially, a network of 17 GAGAN total electron content stations data are considered in the analysis for both quiet and disturbed days. The ionospheric time delay results of the TSE model indicate that the model is performing better for quiet days than the disturbed days. The delay because of the TSE model is compared with that of the delays because of Klobuchar and IRI-2007 models and experimental GAGAN data. The obtained results shows that the TSE model is estimating delay more closely with respect to GAGAN data than that of the Klobuchar and IRI-2007 models and may be considered for use in offline applications.