GNSS
| Back to: | CIRM Knowledge Base |
| Page completeness level: | Medium |
Overview
A global navigation satellite system (GNSS) is a satellite navigation system with global coverage that uses satellites to provide autonomous geo-spatial positioning. It allows small electronic receivers to determine their location (longitude, latitude, and altitude/elevation) to high precision (within a few metres) using time signals transmitted along a line of sight by radio from satellites. The system can be used for providing position, navigation or for tracking the position of something fitted with a receiver (satellite tracking). The signals also allow the electronic receiver to calculate the current local time to high precision, which allows time synchronisation.
Operational GNSS
GNSS Augmentation
Augmentation of a GNSS is a method of improving the navigation system's attributes, such as accuracy, reliability, and availability, through the integration of external information into the calculation process. There are many such systems in place and they are generally named or described based on how the GNSS sensor receives the external information. Some systems transmit additional information about sources of error (such as clock drift, ephemeris, or ionospheric delay), others provide direct measurements of how much the signal was off in the past, while a third group provide additional vehicle information to be integrated in the calculation process.
- Satellite-based augmentation systems (SBAS) support wide-area or regional augmentation through the use of additional satellite-broadcast messages. Using measurements from the ground stations, correction messages are created and sent to one or more satellites for broadcast to end users as differential signal. SBAS is sometimes synonymous with WADGPS, wide-area DGPS
- Ground-based augmentation system (GBAS) / Ground-based regional augmentation system (GRAS) is a system that supports augmentation through the use of terrestrial radio messages. As with the satellite based augmentation systems detailed above, ground-based augmentation systems are commonly composed of one or more accurately surveyed ground stations, which take measurements concerning the GNSS, and one or more radio transmitters, which transmit the information directly to the end user from the ground up thus avoiding the constraints associated with GEO Satellites at high altitudes. See DGPS.
