Study On The Measurement And Calculation Of Crown Parameters Based On Terrestrial 3D Laser Scanning

Forest inventory parameters such as crown projection area and crown volume are critical to the study of single-tree biomass and three-dimensional green biomass.Stumpage’s leaf is the main place that it interacts with the external environment,and its Leaf Area Index measurements on growth,photosynthesis and respiration,as well as the amount of vegetation carbonization of plant are of great significance.The objective of this study is to develop highly precise measurement and calculation methods for crown parameters of single trees based on a terrestrial 3D laser scanning system.In the crown projection area and volume,a total of 20 sample trees with different species were selected,and 3D laser scanning system was used to capture the initial point cloud data of all the sample trees.A series of processing including point cloud registration,denosing,and extraction were carried out to obtain the final point cloud data of single trees.Finally,the proposed improved convex hull algorithms were used to calculate the crown projection area and crown volume of the single trees and compared with the results obtained by the traditional method and geometrical simulation method.Results indicated that the crown projection area(or crown volume)obtained by different methods were strongly correlated,especially for the geometric simulation and improved convex hull algorithms.With regard to the improved convex hull algorithms,the mean of absolute difference in percentage of geometrical simulation-based results was 4.31% for crown projection area,and 4.59% for crown volume,respectively.Meanwhile,the time consumed by the improved algorithms was significantly reduced,which took only 21% of the time required by the traditional measurement method,and 38% of the geometrical simulation method.In the leaf area index,a total of 24 forest plots in the experiment area were selected,and a method of calculating the leaf area index based on the binomial cloud data acquisition is proposed.Laser scanner for the canopy of point cloud data by certain proportion zoom in a ball on the surface,and then through Lambert Azimuthal Equal-Area Projection and the Stereo graphic Projection on spherical images projected onto a plane,in order to get similar hemisphere image,and Finally,the leaf area index is calculated by single angle inversion method and Miller formula inversion method.The leaf area index based on the point data and the leaf area index based on the fish image acquisition are compared and analyzed.The results show that the leaf area index obtained by the Miller formula inversion method based on the Stereo graphic Projection and the leaf area index obtained by Winscanopy software are fitted.The slope of the straight line is 1.039,the coefficient of determination is 0.9895,and the result is more accurate and the precision is higher.