EGNOS is an acronym for European Geostationary Navigation Overlay Service. Like WAAS in North America, EGNOS is an enhancement to GPS in Europe that can allow specially equipped GPS receivers to more accurately calculate their position.
EGNOS uses a network of ground-based stations that compare their precisely known location with locations calculated from GPS satellite signals. Any differences found can be used to create correction data that's broadcast from EGNOS satellites.
EGNOS can help correct for error caused by distortion of GPS signals as they pass through the ionosphere as well as clock and orbital variations associated with individual GPS satellites.
Similar WADGPS systems that cover other parts of the world include WAAS (North America) and MSAS (centered around Japan).
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