Study On Single Tree Measuring Factors Based On Terrestrial Three-dimensional Laser Scanning Technology

With the continuous development of computer technology and three-dimensional laser technology,the application of terrestrial three-dimensional laser scanning technology in forest resource survey has also continued to develop and progress.Terrestrial three dimensional laser scanning can accurately,efficiently and quickly obtain the 3D point-cloud data of trees without damaging trees,so that problems such as tree structure parameters extraction and tree 3D model construction in precision forestry research are well solved.The use of terrestrial three-dimensional laser scanning system to extract single tree parameters has become a hot research topic in the field of forestry measurement,which has broad application prospects.This study results lay a foundation for the rapid,accurate and efficient acquisition of the basic information of tree parameters and timely monitoring the dynamic changes of forest resources,thereby increasing the digital level and automation of forest inventory,reducing the measurement cycle,and improving the digitalization theory and application level of China's forestry to a new level.The main research results of this study include:(1)Calibration and evaluation of three-dimensional laser scanning instrumentsThis study takes the three-dimensional laser scanner Focus3D X130 as the research object,verifies the distance and horizontal angle of the terrestrial three-dimensional laser scanner,and obtains the evaluation results by designing outdoor experiments.Through the experiment,the ranging accuracy of Focus3D X130 is found to be 5mm and measuring horizontal angle accuracy is 0.0101°(2)Single tree parameters extractionA total of 12 sample plots with different forest types and plot shape were selected and a three-dimensional laser scanning system was used to collect the point-cloud data of these plots.After processing the initial data by registration,denoising,and simplification,the point-cloud data for each individual tree was extracted.The traversal array algorithm,least-squares fitting of circle algorithm,and quick convex hull algorithm were programmed in Matlab and applied to extract the tree height and DBH,respectively.The extracted parameters were then compared with the actual measured data.The results showed that the attained correlation coefficients between the extracted values and the actually measured data are respectively 0.9232,0.8952 and 0.9145,while the RMSEs(root mean square errors)are respectively 1.344m,3.179cm and 2.869cm.The comparisons of single-tree parameters extracted in different sample plots indicated that extracted tree height and DBH values for the planted forests were superior to these of the natural forests.In addition,the estimation of DBH was not correlated to the size and shape of the sample plots.(3)The construction of the taper equation model and the solution of timber volumeBased on the established Betula papyrifera standard plots,the appropriate taper equation as an alternative model were selected.Based on the TLS point-cloud data and analytical wood data for model regression and parameter estimation,the taper equation model for Betula papyrifera in the in Dongfanghong Forest Farm were established.At the same time,based on the TLS point cloud data and taper function,we established the taper-timber volume equation.