The GPS Aided Geo Augmented Navigation or GPS and Geo Augmented Navigation system (GAGAN) is a planned implementation of a Satellite Based Augmentation System (SBAS) by the Indian government. (Gagan is the transliteration of a Hindi word that means sky.) It is a system to improve the accuracy of a GNSS receiver by providing reference signals. Being developed jointly by the Airports Authority of India (AAI) and the Indian Space Research Organization (ISRO), the project is being integrated with the geostationary satellite GSAT-4 and has a goal of being operational in 2008.[1][2]

The Indian government has stated that it intends to use the experience of creating the GAGAN system to enable the creation of an autonomous regional navigation system called the Indian Regional Navigational Satellite System (IRNSS) and that it might use the GSAT-4 satellite as a technology demonstration system phase of the proposed navigational system.[3]