GNSS (Global Navigation Satellite System)

GNSS (Global Navigation Satellite System) is the general term for any constellation of satellites that provides positioning, navigation, and timing (PNT) services globally. Four fully operational GNSS systems exist: GPS (US, 31 sats), Galileo (EU, 28 sats), GLONASS (Russia, 24 sats), and BeiDou (China, 30 sats). Regional systems include QZSS (Japan, 4 sats augmenting GPS over Asia-Pacific) and NavIC/IRNSS (India, 7 sats). Modern receivers are multi-GNSS — using signals from multiple constellations simultaneously — which improves accuracy (sub-metre), availability (more satellites visible), and resilience against single-system failures or interference.