Geomagnetic Storm Effects on GPS Aided Navigation over Low Latitude South Indian Region

The Indian Navigation System, GPS Aided GEO Augmented Navigation, 'GAGAN', being designed and developed as a Global Navigation Satellite System, is expected to become operational by 2010. Ionospheric time delay, a function of Total Electron Content (TEC), is the major error source in GNSS. The ionosphere exhibits a peculiar behavior corresponding to large TEC fluctuations in low latitude regions. Further, geomagnetic storms will also produce severe enhancements in the TEC. The TEC values estimated from the SOPAC data archive of the International GNSS Service (IGS) for the low latitude stations, Hyderabad (78.45oE, 17.35oN) and Bangalore (77.51oE, 13.03oN) in the southern region of India during the severe geomagnetic storm period in October 2003 are compared with the TEC values obtained from International Reference Ionosphere 2007 (IRI) empirical model. Such findings would help in developing a region-specific ionospheric empirical prediction model for the GAGAN.