Effect of Quasi Zenith Satellite ( QZS ) on GPS Positioning
Effect of Quasi Zenith Satellite ( QZS ) on GPS Positioning
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发表时间：
2009
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通讯作者：
T. Takasu;T. Ebinuma;A. Yasuda
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作者：
T. Takasu;T. Ebinuma;A. Yasuda
QZS是为了补充日本民用GPS的性能而设计的。它具有与未来GPS、L1-SAIF和实验性LEX兼容的L1C、L2C和L5信号，而不是传统的L1信号。它将于2010年夏天推出。QZS的半长轴为42,164公里，偏心率为0.075±0.015，与赤道的倾角为43°±4°。地球轨道的中心经度为135°E。本文利用软件仿真器进行仿真，对定位精度进行评估。为了研究QZSS对GPS定位的影响，我们模拟了亚洲地区一些站点的GPS和QZS观测数据。为了模拟城市区域的天景，在数据生成过程中加入了FOV模型。通过使用这些数据，我们评估了卫星可见度、PDOP以及单点定位和RTK的性能。在卫星可见度和PDOP方面，没有QZSS的解决方案可用性不到90%。预计在中纬度地区也会有很大的PDOP，只有GPS。同时，额外的QZSS卫星明显提高了解决方案的可用性和PDOP。在单点定位和RTK性能方面，在GPS和QZSS的情况下，与仅使用GPS的情况相比，解算精度有很大的提高。采用QZSS卫星和三频测距信号的RTK也有望达到90%以上的定位率。这些仿真结果清楚地表明了QZS对改善GPS定位性能的效果，特别是在城市峡谷等恶劣环境下。
QZS was designed to supplement the performance of GPS civil use by Japan. It has the compatible signals of L1C, L2C and L5 to the future GPS, L1-SAIF and experimental LEX other than the legacy L1 signal. It will be launched in the summer of 2010. QZS will have a semi-major axis of 42,164 km, eccentricity of 0.075 ± 0.015 and inclination to Equator 43° ± 4°. The central longitude of the earth track is 135°E. In the present paper, positioning accuracy is evaluated by the simulation which uses a software simulator. To investigate the effect of QZSS on GPS positioning, we generate the simulated GPS and QZS observation data at some sites in Asian region. To simulate the sky view in urban area, the FOV model is included in the data generation process. By using these data, we evaluate satellite visibility, PDOP and the performance of single point positioning and RTK. As to the satellite visibility and PDOP, the solution availability is less than 90 % without QZSS. Large PDOP is also expected with only GPS in mid-latitude area. Meanwhile, additional QZSS satellites clearly improve the solution availability and PDOP. For both of single point positioning and RTK performance, solution accuracy is much improved in the GPS and QZSS case comparing to the GPS only case. More than 90 % of fixing ratio is also expected for RTK with QZSS satellites and triple frequency ranging signals. These simulation results clearly show the effect of the QZS to improve the GPS positioning performance especially in sever environment like at urban canyon.