The spread of civil use of the GPS service in car navigation, various surveying and mapping applications, aviation, maritime, and numerous scientific applications, calls for high availability and reliability of the positioning service, which at present has some limitations due to the limited satellite visibility in Taiwan area due to its urban canyons and mountainous regions. Taiwanese geographic feature sometimes causes the interruption of positioning and the degradation of the positioning accuracy due to bad Geometric Dilution of Precision (GDOP). Therefore, the idea of developing the future Taiwanese satellitebased augmentation system is initiated. The proposed constellations have an equatorial plane with four or six MEO satellites, and the tentative altitude of those satellites is set around 20,000 kilometers. Five study sites across Taiwan Island are selected for a fixed-site performance analysis. The objective of this article is to use a GNSS software simulator being developed at the Department of Geomatics, National Cheng Kung University to perform technical benefits analysis for the GPS augmentation using future Taiwanese SBAS. Up to now, the visibility studies against different masking angles of GPS only case, GPS plus four, and GPS plus six have been completed. The preliminary results in term of the satellite visibility do show the potential enhancement of proposed constellations of future Taiwanese SBAS.