In medium Earth orbit (MEO) a satellite sees a far larger part of the Earth than in LEO and stays in view for hours. A few dozen satellites are therefore enough for global coverage — exactly what navigation systems need: at least four satellites in view everywhere, all the time.
| System | Altitude | Period | Inclination |
|---|---|---|---|
| GPS (US) | ± 20,200 km | ± 12 hours | 55° |
| GLONASS (Russia) | ± 19,100 km | ± 11 h 16 min | 64.8° |
| Galileo (EU) | ± 23,222 km | ± 14 h 5 min | 56° |
| BeiDou (China), MEO part | ± 21,500 km | ± 12 h 53 min | 55° |
GLONASS's higher inclination gives better coverage at high latitudes — logical for a country lying largely far to the north. How navigation works and how it is jammed is covered in the EW Academy (§ 14).