摘要
应用地面三维激光扫描仪,在大小兴安岭地区的4块白桦(Betula platyphylla)次生林样地进行单木扫描,对扫描后树干点云进行分层处理并设置阈值;运用Hough变换算法提取单木位置与胸径,利用树干生长方向得到树高与冠幅;运用回归分析对算法估计值和实测值进行拟合,判断算法的准确性;利用体元模拟法与传统体积计算方法分别估测树冠体积,分析两种算法的差异。结果表明:4块样地的单木识别率较高,平均为86.5%;4块样地的单木胸径、树高、冠幅估测的决定系数(R~2),分别为0.82、0.79、0.83,相应的均方根误差分别为2.03 cm、1.98m、0.45 m,显示了较好的估算精度;利用体元模拟法与传统树冠体积计算方法得到4块样地中树冠体积的平均差异为35.6%,两种算法间4块样地平均决定系数为0.96,拟合较好。
Four Betula platyphylla secondary forest plots in the Greater and Lesser Khingan Mountains were scanned by using a ground 3 D laser scanner and the threshold was set after scanning the trunk point cloud. We used Hough transform algorithm to extract the information of tree position and the diameter at breast height( DBH),used the growth direction of the tree trunk to obtain the height and the crown width of the tree,and used regression analysis to fit the estimated value and the measured value to judge the accuracy of the algorithm. Finally,the volume of canopy was estimated by the methods of voxel simulation and traditional volume calculation,respectively,and the differences between the two algorithms were analyzed.The results showed that the average recognition rate of single trees in the four plots was satisfied,about 86%. The determination coefficients of DBH,tree height and crown width of four plots were 0.82,0.79 and 0.83,respectively,and the corresponding root mean square errors were 2.03 cm,1.98 m and 0.45 m,respectively,which shows good estimation accuracy.The average difference of canopy volume among the four plots obtained by the method of voxel simulation and traditional canopy volume calculation was 35.8%,and the coefficient of determination between two methods was 0.96,which was fitted well.
引文
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