What is the distance between the Earth's surface and the motorists' satnav satellites?
For satellite navigation, you are most likely using the Global Positioning System, which uses six planes of satellites at an altitude of 20,180 km. However, many systems can also use the GLONASS satellite constellation to get more satellites visible, especially near the poles. They orbit in three planes at 19,130 km.
You can get a real-time view of some of the constellations at stuffin.space
GPS satellites orbit at an altitude of about 12,550 miles.
However, as GPS is controlled by the US Department of Defense, who can (theoretically) turn it off whenever they want there are various other navigation systems:
- Glonass (Russian). This is in a highly elliptical orbit, so "altitude" is not constant.
- Beidou (China). This constellation utilizes satellites at a number of radically different altitudes.
- Galileo (Europe). These are in a similar, though not identical, orbit to GPS.
Some hand-held satnavs can use multiple satellite systems. I have a Garmin cycle computer that can use both GPS and Glonass.