The Multi-Functional Satellite Augmentation System (MSAS) is a navigation system developed by Japan and some Asian countries to increase the positioning accuracy of the GPS system. MSAS is comparable and compatible with the European EGNOS system and the American Wide Area Augmentation System( WAAS).
Like these, the MSAS system works with correction signals that convert errors in the satellite orbits and errors caused by ionospheric disturbances into correction signals and transmit them to the corresponding GPS receivers. The correction signals are determined using several geostationary satellites and many receiving stations, the Ranging and Integrity Monitor Stations( RIMS).
The positioning accuracy of the GPS system is increased by a factor of about 10 to a few meters by the MSAS system. This positioning accuracy is required above all in air traffic control for landing approaches and poor visibility, since GPS accuracy is not sufficient for these applications.