GPS Global Positioning System
US satellite navigation. 31 satellites in medium Earth orbit. Receiver computes position via time signals from ≥4 satellites (trilateration).
Operational 1978, full constellation 1995, civilly free since 2000 (before that "Selective Availability" degradation). Other GNSS: Galileo (EU, 2011), GLONASS (Russia, 1995), BeiDou (China, 2020). Modern multi-constellation receivers use all simultaneously for better precision. Position ~5 m, with RTK (Real-Time Kinematic) down to cm-level. GNSS = Global Navigation Satellite System (umbrella term).