Today, GNSS (Global Navigation Satellite Systems) positioning relies on several constellations. The exact number varies slightly depending on the source and the status of the satellites (active, in reserve, maintenance), but a reliable order of magnitude can be given (2025–2026): Main constellations (global coverage) • GPS (United States): ~31 active satellites • GLONASS (Russia): ~24 operational satellites • Galileo (Europe): ~27 operational satellites (≈30 in orbit) • BeiDou (China): ~35 satellites (current order of magnitude for the complete constellation) Total global GNSS In practice, this equates to approximately 110 to 120 active satellites used for global positioning. The system with twenty-four satellites was fully operational in 1995. Knowing the satellite positions at the time the signals were transmitted, and the measured pseudo-distances (possibly corrected for various factors.