Tree Height and Diameter Extraction with 3D Reconstruction in a Forest based on TLS

In view of the low accuracy of Tree Height(TH) and Diameter at Breast Height(DBH) estimation，as well as the difficulty of individual tree modeling in dense forest，a method to extract forest structure parameters(TH and DBH) and reconstruct a Three-Dimensional(3D) model of forest in subtropical environment based on TLS point cloud data is proposed.The first step is to apply a multi-scale method to extract the ground points for the generation of Digital Elevation Model(DEM).Secondly，using similarity of principal direction between neighboring points and distribution density of points，trunk and other plant organs are separated.Next the trunk points are processed to automatically estimate the tree position and DBH by iterative least squares cylinder fitting;the tree height is automatically estimated by using the octree segmentation.Finally，by combining with the technology of individual tree modeling，a plot-scale 3D forest scene has been reconstructed by planting individual tree model on the terrain model iteratively.The results showed that the correlation coefficient of DBH is R²=0.996，and the average relative error was 2.09%，RMSE was 0.66 cm;the correlation coefficient of tree height is R²=0.972，and the average relative error was 2.16% with RMSE of 0.92 m.The plot-scale reconstructed 3D model of the forest can express the true shape of forest.