2-D electron density profile of the ionosphere using the modified spherical harmonic analysis

The advent of Global Positioning System (GPS) has revolutionized the field of navigation particularly in the field of civil aviation sector. The GPS is a reliable, all weather satellite-based radio navigation system that provides accurate three dimensional (3D) navigation solution i.e., position, velocity and timing information, up to 10 seconds anywhere on or above the earth’s surface. But the accuracy of the navigation solution is affected by several factors such the satellite-receiver geometry configuration, refraction of the GPS signal in Ionosphere and Troposphere, multi path and solar activity. Out of all, the refraction of the GPS signals in ionosphere that introduces a delay in the ranging information, significantly influences the navigation solution accuracy. The effect of the ionospheric delay on navigation solution accuracy can be estimated precisely by constructing the electron density profile of the ionosphere. In this paper, electron density profile of the ionosphere is constructed using the tomographic technique at 11:15:00 Hrs of 22 July 2009 using the data due to the dual frequency GPS receiver located at IISc, Bangalore.