多视几何无人机影像堆体体积量算

Volumetric calculation of multi-vision geometry UAV image volume

针对形态不规则、大规模或不便于近距离实测的堆体体积的计算问题,借助低空无人机(Unmanned Aerial Vehicle,UAV)搭载非量测的普通数码相机对堆体进行倾斜摄影,获取堆体多视角的倾斜影像。利用运动恢复结构和基于面片的多视角立体视觉(Sf M-PMVS)技术处理由无人机获取的倾斜影像。在引入地面像控点后,首先对影像进行特征点提取和基于最近邻距离比率(Nearest Neighbor Distance Ratio,NNDR)算法的SIFT粗匹配,采用随机抽样一致算法(Random Sample Consensus,RANSAC)剔除误匹配点对进而精确求得影像的基本矩阵F完成影像匹配。引入经相机检校得到的相机内参数精确求解本质矩阵E,恢复相机运动姿态后由投影矩阵P计算稀疏点云在物方坐标系下的坐标,采用PMVS算法进行点云密集匹配,经光束法平差后得到堆体在物方坐标系下精确的三维密集点云。对三维密集点云做点云分割,剔除非堆体表面点后构建Delaunay三角网,利用数字地面模型(Digital Terrain Model,DTM)法计算堆体的体积。与用GNSS-RTK均匀测得堆体表面三维坐标点采用DTM法计算堆体体积的结果对比证明,所给方法计算堆体的体积在准确性上能满足实际生产中的要求。

For the calculation of stack volume with irregular shape,large scale or inconvenient close-range measurement,this paper studies the tilt photography of the stack by using a non-measured ordinary digital camera with UAV.A tilted image of the multi-view of the stack is obtained.The tilted image acquired by the drone is processed using the structure from motion and patch-based multi-view stereo(SfM-PMVS)technique.After the introduction of the ground image control point,the feature point extraction and the SIFT rough matching based on the nearest neighbor distance ratio(NNDR)algorithm are firstly applied,and the random sample consensus(RANSAC)is used to eliminate the mismatched point and then accurately obtain the basic matrix F of the image to complete image matching.The in-camera parameters introduced into the calibration are used to accurately solve the essential matrix E.After the camera pose is restored,the coordinates of the sparse point cloud in the object coordinate system are calculated by the projection matrix P,and the point cloud is closely matched by the PMVS algorithm.Obtain a precise three-dimensional dense point cloud of the stack in the object coordinate system,conduct point cloud segmentation on the 3D dense point cloud,and build a Delaunay triangulation after the non-stacked surface point of the stack is eliminated.The volume of the pile is calculated by the Digital Terrain Model(DTM)method.The calculation results of this method are compared with that of using DTM method to calculate the volume of the pile by GNSS-RTK for uniformly measuring the three-dimensional coordinates of the surface of the stack.It is found that the volume of the pile can meet the accuracy of the actual production.