MTSAT Satellite Augmentation System (MSAS)  is a Japanese Satellite Based Augmentation System (SBAS ), ie a satellite navigation system that supports GPS differentiation (DGPS) designed to supplement the GPS system by reporting Of those signals. Tests have been accomplished successfully, MSAS for aviation was commissioned on September 27, 2007.
A similar service is provided in North America by Wide Area Augmentation System (WAAS), and in Europe by European Geostationary Navigation Overlay Service (EGNOS).
Through the use of these Augmentation Systems an individual GPS receiver is able to correct its own position, offering a much more accuracy. Typically GPS signal accuracy is improved from some 20 meters to approximately 1.5-2 meters in both horizontal and vertical dimensions. 
|Satellite Name & Details||NMEA / PRN||leasing|
|MTSAT-1R||NMEA # 42 / PRN # 129||140 ° E|
|MTSAT-2||NMEA # 50 / PRN # 137||145 ° E|
- Multi-Functional Transport Satellite (MTSAT)
- Quasi-Zenith Satellite System (QZSS)
- Jump up^ http://www.unoosa.org/pdf/icg/2008/icg3/08-1.pdf
- Jump up^ “Wide Area Augmentation System” . Archived from the original on June 12, 2007.