Leaf Area Index Research Based On Laser Point Cloud

Vegetation canopy is the main place where trees interact with natural environment, and the research of canopy parameters has great significance to the analysis of trees. Photosynthesis,respiration and transpiration of the trees and the interception of precipitation occurs mostly in tree canopies. Vegetation canopy structure parameters is an important index to reflect the growth status of trees, to assess the carbon storage and carbon sink capacity assessment trees,leaf area index is one of the most important parameters in crown layer parameters. Traditional measuring method of leaf area index is usually need to consume a lot of time and manpower,and always have devastating effects on the vegetation in the measurement. In order to measure leaf area index of vegetation canopy more convenient, quickly, reliable, and non-destructively,this investigate regards a single plant and multi-trees as the research object, uses the HemiView canopy analyzer and three-dimensional laser scanner to obtain color digital images and three-dimensional point cloud data, and designs graphics algorithm and builds forestry index,and then gets the key parameters of stand. Specific work is as follows:The first part is forest stand leaf area index calculation. In order to obtain canopy leaf area index more accurately, this Investigation presents a method that hemispherical photography was applied to laser point cloud data. For color digital images from fish eye camera, effective leaf area index(eLAI) and cluster index(CI) can be obtained according to the law of Beer-Lambert,and then true leaf area index(aLAI) can be obtained. The three-dimensional point cloud data from laser scanner are scaled on the unit sphere of hemisphere on the surface, and then the half spherical images are projected in the plane through the projection algorithm to get hemisphere image. The remaining work are completed according to the method of hemispherical.The second part is the research of blade separation. This investigating proposes a new type of measuring leaf area index based on laser point cloud. The three-dimensional point cloud data of an individual stumpage are obtained through the ground laser scanner. The model of blade is established to extract the veins and to cluster the veins. Watershed algorithm is employed to segment formalized point cloud data, and makes the segmentation of each little space contains only a vein, so as to realize the separation of the blades. Finally, each blade is projected to the horizontal plane and is triangulated to calculate the leaf area, finally the leaf area index is calculated.Finally, the leaf area index of the stand and single plant are given. In the study of stand, the results of hemispherical photography method and three-dimensional point cloud method are contrasted and prove that hemispherical photography method can be applied to three-dimensional point cloud data reasonably. In the study of blade separation, the blade was the separation and leaf area index of the trees are drawn.The research of leaf area index access is very important from the viewpoint of practicalapplication. In the future study, leaf area index obtained from laser point cloud will be widely used;...