- Navigation satellites transmit precise timing signals and orbital data (ephemeris), allowing receivers to calculate position via multilateration.
- Receivers use additional satellites to correct internal clock inaccuracies, essential for meter-level accuracy due to the speed of light.
- Different GNSS systems (GPS, Galileo, GLONASS, BeiDou) use varied orbital and clock correction methods, with Galileo and BeiDou updating more frequently.
- The July 2019 Galileo outage occurred when control center equipment malfunctioned stopped regular updates, causing ephemeris to become ambiguous after 3.5 days due to missing week numbers.
- GLONASS uniquely employs Moscow time and encodes satellite position via integration of motion equations, including gravitational perturbations.
- Each GNSS broadcasts its offset from UTC and handles leap seconds; dual-frequency receivers can virtually eliminate ionospheric errors.
- The Galmon project openly monitors all navigation satellites, displaying real-time data on parameters like IOD, ephemeris age, SISA, and pseudorange residuals.