QZSS (Quasi-Zenith Satellite System) is a Japanese satellite navigation system that consists of space segment and ground segment. In space segment, there are several QZS (Quasi-Zenith Satellite) whose orbit is designed that one QZS out of several satellites always exists near zenith over Japan at least. QZSS also has slightly elliptical and highly inclined orbits in different orbital planes. The eccentricity is about 0.075 and inclination is about 41 degrees which optimized for the middle latitude area like Japan. The benefit of QZSS is that QZSS can provide a seamless service from a high elevation angle to improve the positioning availability in downtown and mountainous areas. Users in Japan, therefore, can observe one QZS at more than 60 degrees elevation angle, and especially, users in main island of Japan can receive a QZS signal from more than 70 degrees. QZSS signals from high elevation angle can provide substantially better positioning availability than that of GPS alone.
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