Tree Modeling And Analysis Based On Terrestrial Laser Scanner Point Cloud Data

Terrestrial Laser Scanner(TLS)can quickly and widely obtain the three-dimensional position information of the tree surface,which has the advantages of high scanning accuracy and rich information.It is widely used in the study of tree morphological structure and parameter extraction.The main content of this thesis is to study and analyze the method of generating tree models based on the point cloud data obtained by TLS.this paper had mainly two parts.In one part of the scheme verification,a simulation TLS point cloud method based on tree model is proposed.In the implementation part of the plan,an apricot volume analysis method based on TLS point cloud and Quantitative Structural Model(QSM)is proposed.The simulation TLS point cloud method based on tree model mainly included four parts.Firstly,set the scanner position and scanning parameters(horizontal and vertical angular interval)to generate all laser beams;secondly,calculate the spatial bounding box according to the size of the tree,and filter out all laser beams passing through the spatial bounding box,that is,it may be compared with the tree model Intersecting laser beams;then,considering the observation conditions,determine the triangular mesh facing the scanner;finally,calculate the intersection of the laser beam and the triangular mesh to generate simulated point cloud.The test models included field-measured tree models and Speed Tree models The RIEGL VZ-400 TLS scanner was used to obtain point clouds of Fraxinus pennsylvanica,Ginkgo biloba L,and Amygdalus davidiana(Carrière)de Vos ex Henr to construct field-measured tree models,and 10 virtual tree models were generated using Speed Tree software to verify the method.It is verified by experiments that the experimental simulation point cloud could match the Speed Tree models and the field-measured point cloud.This method is feasible and has good simulation accuracy.The apricot volume analysis method based on TLS point cloud and QSM mainly included three parts.Firstly,segment the point cloud data,that is,the topological reconstruction of the tree branch structure.Secondly,use the construction method of cover set to gradually form the surface of the tree;divide the obtained surface set into stems and individual branches.Finally,the least squares fitting method is used to reconstruct the surface of the tree as a collection of cylinders of different sizes,which are fitted to approximate the trunk and branches of the tree.The RIEGL VZ-400 3D terrestrial laser scanner was used to scan the five apricot trees respectively at six stations,with three stations in the leaf state and three stations in the leafless state.The QSM method was used to model the fusion data of five apricot trees with and without leaves.At the same time,the branch diameters of five apricot trees were measured on the spot to calculate the volume,and the volume was compared with the volume obtained by QSM modeling.The results show that this method has good accuracy for tree modeling and analysis,but leaves and twigs will affect the modeling,thereby reducing the accuracy of volume estimation.In general,the application effect of TLS in this article is good,which can help improve the efficiency and accuracy of tree modeling and volume analysis.