不同截止高度角下多模伪距单点定位精度分析
Accuracy Analysis of Multi-Mode Pseudo-Range Single Point Positioning under Different Cut-Off Height Angles

针对在卫星信号易被遮挡的复杂环境下，单GPS系统可见卫星数少、卫星几何构型较差、定位精度不高以及历元可用率较低的问题，本文基于WHU2站的实测数据，对不同截止高度角(7？、10？、15？、20？、30？、40？)下不同卫星导航系统组合模式(GPS、GPS/Galileo、GPS/QZSS、GPS/BDS、GPS/Galileo/BDS、GPS/QZSS/BDS、GPS/Galileo/QZSS/BDS)进行多模伪距单点定位解算和数据处理分析。结果表明，随着截止高度角的增加，可见卫星数逐渐减少，PDOP逐渐变大且波动剧烈，定位偏差逐渐变大且稳定性逐渐变差，历元可用率也逐渐降低，组合系统对单系统的精度改善率逐渐提高。相比于其他卫星模式，特别是单GPS系统，多系统组合GPS/Galileo/QZSS/BDS具有更优的定位性能，即当截止高度角为7？时，历元可用率高达100%，定位精度优于4 m，改善率达21.8%；当截止高度角为40？时，历元可用率仍有98.9%，定位精度优于6 m，改善率达27.8%。
In some complex environment where satellite signals are blocked, single GPS system has few visible satellites, poor geometric configuration of satellites, low positioning accuracy and epoch availability rate. Based on the measured data of WHU2 station, under different cut-off angles (7？, 10？, 15？, 20？, 30？, 40？) different combination modes of satellite navigation systems (GPS, GPS/Galileo, GPS/ QZSS, GPS/BDS, GPS/Galileo/BDS, GPS/QZSS/BDS, GPS/Galileo/QZSS/BDS) for multi-mode pseudo- range single point positioning are calculated and analyzed. The results show that with the increase of the cut-off height angle, the number of visible satellites decreases gradually, with the PDOP becoming larger and fluctuating sharply. Meanwhile, the positioning deviation becomes larger and the stability becomes worse, and the epoch availability rate decreases gradually. The accuracy improvement rate of multi-system to single system also increases gradually. Compared with other satellite modes, especially single GPS system, the multi-system combination GPS/Galileo/QZSS/BDS has better positioning performance. When the cut-off height angle is 7？, the epoch availability rate is up to 100%, and the positioning accuracy is better than 4 m, with the improvement rate up to 21.8%. When the cut-off height angle increases to 40？, the epoch availability rate is still 98.9%, and the positioning accuracy is less than 6 m, with the improvement rate as 27.8%.