Glossary:GNSS
GNSS or Global Navigation Satellite System is an umbrella term for the several satellite-based Position, Navigation and Timing (PNT) systems. The core systems are GPS (United States), GLONASS (Russian Federation), Galileo (EU) and BeiDou (China). They all rely on the fact that you can determine your latitude, longitude, altitude and the time by comparing the relative delays of highly accurate timing signals from at least 4 satellites within direct line of sight.