GNSS Augmentation

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Augmentation of a Global Navigation Satellite System (GNSS) is a method of improving system attributes such as accuracy, reliability, and availability through the integrated 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 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.

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[edit] Satellite Based Augmentation System

A Satellite Based Augmentation System (SBAS) is a system that supports wide-area or regional augmentation through the use of a satellite-broadcast message. Such systems are commonly composed of multiple ground stations, which take measurements concerning the GNSS, and one or more satellites, which broadcast the information to the receivers.

While SBAS designs and implementations may vary widely, with SBAS being a general term referring to any such satellite-based augmentation system, under the ICAO a SBAS must transmit a specific message format and frequency that matches the design of the United States' Wide Area Augmentation System.[citation needed]

[edit] Various Implementations

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

[edit] Ground Based Augmentation System

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. Such systems are commonly composed of one or more 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 20km, and transmitting in the Very High Frequency (VHF) or Ultra High Frequency (UHF) bands. Where-as GRAS is applied to systems that support a larger, regional area, and transmit in the Low frequency (LF) and Medium frequency (MF) bands.[citation needed]

[edit] Various Ground Based Augmentation Systems

[edit] Various Ground-based Regional Augmentation Systems

[edit] Additional Navigation Sensors

The augmentation may also take the form of additional information being blended into the position calculation. Many times the additional navigation sensors operate via a different principle than the GNSS and as such are not necessary 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:

[edit] References

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