This mega thrust earthquake of Dec 26, 2004 shifted several sites on Indian and Eurasian plates, which has been quantified from various GPS studies. As the relative change in triangular area between different sites is more sensitive than the relative change in their coordinates, it has been attempted to calculate the anomalies in triangular area on daily basis between 12 permanent GPS stations of C-MMACS and 16 IGS stations for a period of 60 days from 1st Dec 2004 – 30th Jan 2005.

GNSS is a global navigation satellite system comprising of network of satellites that transmit ranging signals used for positioning and navigation anywhere around the globe; on land, in the air or at sea. The US Global Positioning System (GPS/Navstar GPS), the Russian Global Navigation Satellite System (GLONASS) and the upcoming European GALILEO system, Data communications satellites with navigation payloads and Augmentation systems are all part of GNSS.