Characteristics of SBAS grid sizes around the northern crest of the equatorial ionization anomaly

The region around the crests of the EIA accounts for the highest values of TEC and its steep gradients, which introduces high values of range-errors on GPS signals and degrade the position-fixing accuracy of an SBAS. As the TEC gradient is sharper on the poleward side rather than towards the magnetic equator, grid sizes should be different on either side of the crest of the EIA. The present paper highlights the necessity for a differential grid size around the northern crest of the EIA using data recorded from stations under the Indian SBAS GAGAN during the moderate sunspot number year 2004.

► Estimation of grid size for the Indian SBAS during a moderate sunspot number year.
► Estimated grid size is significantly different from that specified by ICAO.
► Results point to a necessity for measurement of TEC at higher spatial resolution.