Satellite Based Augmentation System (SBAS)

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What is the System in use in Europe for satellite systems?

What are the three segments of SBAS?

What error corrections are done in SBAS.

Notes There are four systems in use or in development:

European Geostationary Nav Overlay system (EGNOS)

Wide Area Augmentation System (WAAS) used by the USA

Multi Functioning satellite Augmentation system (MSAS) used by Japan

Geostationary and GPS augmentation Navigation (GAGAN) used in India

Used for Navigation over large areas

Can provide CAT I Approach

The GPS signal error is measured at the reference station.

There are 3 Segments:

Space Segment

Use of NAVSTAR or GLONASS constellations and 3 further geostationary satellites an orbit at about 35 800ft.

Ground Segment

4 mission control centres

6 regional control centres

34 Reference Stations.

User Segment

This is all service users

The use of the atomic clock, ephemeris and clock timing can calculate error for each satellite.

EGNOS improves GPS accuracy to 1 - 2 metres horizontally and 3 - 5 metres vertically.

A Hatch Filter is used to compensate for Ionospheric errors.

NAVSTAR can take up to 3 hours to report a failed system while the use of EGNOS can do it in about 6 seconds.

Summary SBAS is a system where the error checking is completed at the satellite. Depending on where in the world the aircraft a different system can be used, in Europe this system is called EGNOS and improves the accuracy of the satellites and error reporting. SBAS can be used for CAT I ILS Precision approaches but does not provide sufficient accuracy for full ILS approaches.