Global navigation satellite systems (GNSS) provide geospatial positioning (latitude, longitude, elevation) to users on Earth.
This capability is usually ensured by constellations of 20 to 30 satellites in medium Earth orbit (MEO) at around 20,000 km above Earth’s surface. By combining the signal emitted from at least four satellites, and thanks to atomic clock time precision, relativity theory and trilateration techniques, a user’s device can provide the time and location with a precision of a dozen meters up to a few centimeters.
Four constellations are currently able to provide global coverage: BEIDOU (China), GALILEO (European Union), GLONASS (Russia), and GPS (United States of America).
Geospatial positioning is an important capability for climate action as it is used to map areas on Earth and track changes (such as ice mass levels, or ground levels). It is also an enabler of numerous technologies important to mitigate causes of climate change or adapt to its consequences, from logistics networks to city mapping and agriculture optimization. Less frequently, satellite navigation can be used to measure pressure, temperature, as well as water vapor levels, as these atmospheric properties affecting the propagation of the navigation signal.