Satellite-based augmentation system (SBAS) broadcasts corrections of Global Navigation Satellite System (GNSS) ionosphere errors in addition to satellite orbit and clock errors via geostationary satellites. In this study, we studied five systems: Wide Area Augmentation System (WAAS) in the USA, European Geostationary Navigation Overlay Service (EGNOS) in Europe, MTSAT Satellite Augmentation System (MSAS) in Japan, GPS-Aided Geo Augmented Navigation (GAGAN), and System for Differential Correction and Monitoring (SDCM) in Russia. Each SBAS service has its own message structure design to accommodate the service area and satellite communication link budget, resulting in some differences in the sampling rate and the signal acquisition time. Especially, it was noted that SDCM does not transmit correction information for some GPS satellites. The reason is that it provides GPS-related error messages in addition to GLONASS messages, so the bandwidth is somewhat limited. Because of this, there are instances where the minimum number of satellites cannot be secured for GPS-only positioning with SDCM. In this study, we decoded messages obtained from the above-mentioned five services. We selected two International GNSS Service (IGS) site for each SBAS service area, thus the evaluation was conducted for 10 sites. The precise coordinates are needed for the performance evaluation and they are obtained through an on-line GNSS processing service called Automatic Precise Positioning Service (APPS). As a result, we achieved about 40-50 % improvement in positioning accuracy from those of Standard Point Positioning (SPP) positioning.

Keywords: SBAS, GNSS, point positioning