GNSS augmentation

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Augmentation of a global navigation satellite system (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 system[edit]

A satellite-based augmentation system (SBAS) is a system that supports wide-area or regional augmentation through the use of additional satellite-broadcast messages. Such systems are commonly composed of multiple ground stations, located at accurately-surveyed points. The ground stations take measurements of one or more of the GNSS satellites, the satellite signals, or other environmental factors which may impact the signal received by the users. Using these measurements, information messages are created and sent to one or more satellites for broadcast to the end users. SBAS is sometimes synonymous with WADGPS, wide-area DGPS.[1]

Implementations[edit]

Service areas of satellite-based augmentation systems (SBAS).

For details on how various SBAS are implemented, please see the following articles:

Ground-based augmentation system[edit]

Each of the terms ground-based augmentation system (GBAS) and ground-based regional augmentation system (GRAS) describe 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.

Generally, GBAS networks are considered localized, supporting receivers within 20 kilometres (12 mi), and transmitting in the very high frequency (VHF) or ultra high frequency (UHF) bands. GRAS is applied to systems that support a larger, regional area, and also transmit in the VHF bands.[4]

Various ground-based augmentation systems[edit]

  • International Civil Aviation Organization Ground-Based Augmentation System applies to precision approach landing of civil aircraft. Originally this system was called the Local Area Augmentation System (LAAS)
  • The US Nationwide Differential GPS System (NDGPS), An augmentation system for users on U.S. land and waterways.[5]
  • See also, the Differential GPS (DGPS) Wikipedia page

Additional navigation sensors[edit]

The augmentation may also take the form of additional information being blended into the position calculation. Many times the additional avionics operate via separate principles than the GNSS and are not necessarily subject to the same sources of error or interference. A system such as this is referred to as an aircraft-based augmentation system (ABAS) by the ICAO.

The additional sensors may include:

See also[edit]

References[edit]

External links[edit]