Effect of Grid Size Variation on the Interpolation of the Total Electron Content over the Indian Region

Satellite Based Augmentation Systems (SBAS) for navigational services rely heavily on the accu- rate estimation of the Total Electron Content (TEC) along the slant ray path. The Wide Area Augmentation Sys- tem (WAAS) estimates and transmits the delay corrections by assuming a 5x5 degree ionospheric grid (in lati- tude and longitude) at 350 km altitude using a single shell model. The user interpolates these delay values at hislher position using bilinear interpolation. In this paper, the effect of the variation of grid size on the interpo- lation of the TEC is analyzed using TEC data from the year 2005. It is observed that the reduction of grid size from 5x5 to I xl degree and the choice of Kriging technique to interpolate the TEC both at the IGP as well as at the user side result in more accurate estimation of the delay for the GPS Aided Geo Augmented Navigation (GAGAN) system over the Indian region.