What is the GAGAN?

There are many kinds of GPS used worldwide, such as GPS/GNSS/Galileo/Beidou. GPS is most popular worldwide, GNSS is mainly used in Russia, while Galileo is well known in Europe, Beidou is widely used in China. So what is GAGAN? The GPS-aided GEO augmented navigation is an implementation of a regional satellite-based augmentation system (SBAS) by t...