北斗PPK技术辅助无人机航空摄影测量精度分析

Precision analysis of aerial photogrammetry assisted by BeiDou PPK technology

由于受网络信号和基线长度限制,在南北极、远岸岛礁等地区,常用的GPS RTK技术无法应用于无人机航空摄影测量,且GPS并非我国自主的卫星导航系统,无法确保永久安全可靠。为此,本文探索利用我国自主建设的北斗三号全球卫星导航系统(BDS-3),通过动态后处理(PPK)技术辅助无人机摄影测量,以解决上述问题。以大疆精灵4 RTK无人机为例,分别利用BDS-3、GPS及BDS-3+GPS组合观测值,对无人机POS数据进行PPK处理,分析在无地面控制点条件下,不同导航卫星星源对无人机航空摄影测量平面和高程精度的影响。结果表明:利用BDS、GPS、BDS+GPS组合对无人机单点定位POS数据进行PPK处理后,空三加密点平面定位精度由分米级提升至厘米级,高程精度由米级提升至分米级甚至厘米级,与引入5个地面控制点的定位精度相当。北斗PPK技术辅助无人机航空摄影测量满足平原地区1∶500比例尺空中三角测量加密精度要求。

Due to the limitation of network signal and baseline length,the commonly used GPS real-time kinematics(RTK)technology cannot be applied to UAV aerial photogrammetry in areas such as the Arctic and Antarctic,offshore islands or reefs.Moreover,GPS is not our autonomous satellite navigation system,and cannot ensure permanent safety and reliability.To solve these problems,this article explores the use of our self-built BDS-3 to assist UAV photogrammetry through dynamic post-processing(PPK)technology.Taking DJI Phantom 4 RTK UAV as an example,the paper carries out PPK process of UAV POS data with BDS-3,GPS and BDS-3+GPS combined observation values.Then it analyzes the effects of different navigation satellite sources on the horizontal and elevation precision of UAV aerial photogrammetry in the absence of ground control points.The results show that after PPK calculation of the UAV POS data with BDS,GPS and BDS+GPS combination,the horizontal positioning precision is improved from decimeter level to centimeter level,and the elevation precision is improved from meter level to decimeter level or even centimeter level,which is equivalent to that of setting five ground control points.UAV aerial photogrammetry assisted by BDS PPK technology is able to meet the accuracy requirements of 1∶500 scale aerial triangulation encryption precision in plain area.