Investigation of suitability of grid-based ionospheric models for GAGAN

The GAGAN system is planned for air-navigation over the Indian service region. As India comes essentially under the low-latitude region, where the ionospheric behaviour is highly dynamic, the grid-based ionospheric models suitable for mid-latitude regions are not appropriate. The primary tasks in developing an ionospheric model for GAGAN are to take total electron content (TEC) measurements at fixed reference stations using dual frequency GPS receivers and combine them in real-time to estimate the current state of the ionosphere. The estimated vertical delays using six prominent grid-based ionospheric models for the multiple TEC stations data corresponding to quiet days and a disturbed day are presented and compared.