These acronyms refer to a capability found on higher specification GPS chartplotter units, with each of the three effectively offering the same service in different parts of the world.
EGNOS - European Geostationary Navigation Overlay Service (Western Europe)
MSAS - Multi-functional Satellite Augmentation System (Japan and East Asia)
WAAS - Wide Area Satellite Augmentation System (North and Central America)
These services augment the GPS service in their respective areas by reporting on the accuracy and reliability of the GPS signals and as a result increase the accuracy of compatible receivers from around 15 metres to on average 1 to 2 metres. Each system is made up of a combination of geostationary satellites and ground stations, and transmits a signal containing information on the reliability and accuracy of the positioning signals sent out by GPS. These are in turn transmitted to suitably equipped GPS receivers thereby enabling them to display the updated position information.
For more information and details on coverage, go to:
EGNOS - http://www.esa.int/esaNA/egnos.html
WAAS - http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/waas/
MSAS – www.mlit.go.jp
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