GNSS卫星可见性及可用性的概率特征

Probability statistics of GNSS satellites visibility and availability

针对现有平均值指标难以客观地评价具有显著非对称非均匀的全球导航卫星系统可见性及可用性的问题,该文利用概率统计方法和广播星历研究了北斗导航系统、全球导航卫星系统和格洛纳斯系统的可见性及可用性的概率分布特征。结果表明:可见星数、站星高度角及可跟踪因子、几何精度因子值的概率直方图均呈显著的非对称非均匀分布特征。中地球轨道卫星可见概率与高度角为近似线性负相关,随方位角呈现"四叶玫瑰"对称非均匀分布特征且南北向可见概率略高于东西向。北斗导航系统静止地球轨道、倾斜地球同步轨道卫星远高于中地球轨道卫星的可跟踪因子,显著提高了导航星座时间可用性。星空分布图与几何精度因子值均表明导航性能随纬度增大而降低。此外,全球定位系统和全球导航卫星系统在可见性及可用性概率特征基本一致,而北斗导航系统概率分布特征与之具有较高的互补性且在亚太地区较之更适用于受限应用条件。

The defect of existing evaluation methodology for satellites navigation performance evaluation was explicitly illuminated in this paper.Both probability statistics and GNSS broadcast ephemeris were employed for analyzing probability distributions of GPS,BDS and GLONASS satellites visibility and availability.The probability histograms plotted by the number of visible satellites,elevation of satellites,tracked time-factor and GDOP illustrated that the probability distribution was extremely asymmetric and nonhomogeneous.The probability of visible MEO satellites had a negative linear correlation with satellites＇ elevations,and the feature along the azimuth angle was characterized by special four-leaf-rose which meant the probability along North-South was a little higher than that along East-West.The tracked time-factor of MEO satellites was much lower than that of GEO and IGSO satellites which improved the time availability of the constellation significantly.The sky distribution of GNSS satellites and GDOP results showed that the navigation performance decreased with the increase of latitude.In addition,GPS had a similar navigation performance with GLONASS which were highly complementary to BDS,and in the Asian-Pacific region BDS had its natural advantage with GPS and GLONASS under limited observation condition（such as big mask-off elevation angle and wide shielding azimuth）.