Q 4.3 Give an overview of GAGAN satellite based navigation system.

GAGAN, an acronym of GPS Aided Geo Augmented Navigation system (GAGAN) is a satellite based augmentation system (SBAS) serving India. It has been developed by the Indian Space Research Organization in collaboration with Airport Authority of India for applications in the Indian region to enhance accuracy of GPS fixes to a level that can support safety-critical applications.
Accuracy is improved by utilizing an additional GPS-like radio transmission from a geostationary satellite. The overlaid transmissions provide independent ranging signals, system data and error corrections.

Suryanarayan, K.N., “GAGAN – The Indian satellite based augmentation system” Indian Journal of Radio and Space Physics, Vol 36, August 2007, pp 293-302.