What is Global Navigation Satellite System (GNSS)?
A global navigation satellite system (GNSS) is a type of satellite navigation system that provides global coverage. A GNSS is defined by a constellation of satellites working in orbit and working with a network of ground control stations and receivers that compute ground positions through an adapted version of trilateration.
To date there are only two operational GNSSs, the United States' Global Positioning System (GPS) NAVSTAR and the Russian Federation's Global Navigation Satellite System (GLONASS). However, there are two other satellites in development, the European Union's Galileo and China's Compass or BeiDou-2.
A global satellite navigation system is a constellation of satellites that autonomously provide geospatial positioning for many devices, enabling electronic devices with the appropriate receivers to determine their exact position on the earth's surface.
The initial motivation for a satellite system was for military applications, but it has now advanced to more extensive civilian applications, including the following:
- Disaster warning and emergency response
- Land transport
- Mapping and surveying
- Monitoring the environment
- Precision farming
- management of natural resources
- Research such as climate change and ionospheric research
- Wireless networking
- Photographic geocoding
- Mobile satellite communication
- Precise time reference
- Military precision ammunition
In general, global coverage can be achieved by a satellite constellation of 20 to 30 mid-earth orbit (MEO) satellites. Each satellite would be placed between multiple orbital planes. The current systems vary, but set the overall orbital inclinations to> 50 ° and their orbital times to approximately 12 hours at an altitude of almost 12,000 miles (20,000 km).