Research On 3D Reconstruction Of Jujube Tree Crown Based On Lidar

Chinese jujube is a kind of fruit planted in large area in China,which has high economic and ecological value.With the continuous expansion of jujube planting area in Xinjiang,problems such as labor shortage,high labor intensity,low efficiency and increased cost become more and more serious.It is urgent to realize the delicate operation of intelligent jujube plantation management machinery such as intelligent pruning and targeted spraying.Among them,the most important precondition to realize intelligent pruning of jujube is to carry out threedimensional reconstruction of target object.In this paper,by comparing the research status of three-dimensional information acquisition technology and reconstruction technology at home and abroad,combining the planting mode of dwarf and dense-planted jujube orchard in Xinjiang and the three-dimensional structure characteristics of jujube trees,a measuring platform for jujube tree contour is designed and built with laser radar as a scanning device to realize data acquisition of jujube point cloud.Then,point cloud pretreatment,jujube extraction and jube trees are designed.Three-dimensional reconstruction of jujube tree is realized by contour reconstruction and branch reconstruction algorithm.Specific research is as follows:Field investigation of jujube planting mode and three-dimensional structure measurement of jujube.The planting mode and three-dimensional structure of jujube are the important basis for determining the relevant parameters of three-dimensional structure of scanning platform and three-dimensional reconstruction algorithm.The row spacing and plant spacing of jujube are obtained by investigating the dwarf and dense planting mode of jujube orchard.The average tree height,East-West crown width and South-North crown width of 3-year,5-year and 8-yearold jujube trees are obtained;the diameter and inclination of jube branches in different height areas are obtained.Design of 3-D scanning platform for jujube crown.According to field research results and two-dimensional Lidar ranging principle,a three-dimensional scanning platform of jujube crown is designed in the form of horizontal straight movement.Through two-station scanning on both sides of jujube row,the jujube point cloud is obtained.The platform scans single crosssection of jujube tree with two-dimensional lidar,completes three-dimensional scanning of jujube tree with two-dimensional lidar linear motion driven by electric sliding rail,then designs acquisition software of the scanning platform according to hardware structure parameters of the scanning platform,realizing acquisition of jujube point cloud.Pretreatment and extraction of jujube point cloud.According to the results of field research and scanning platform,point cloud data of single jujube tree were processed to obtain point cloud.First,remove most of the redundant points in the scanned scene through straight-through filtering,ground filtering and statistical outlier filtering algorithm to remove the drift points and complete the pre-processing of jujube point cloud;secondly,overcome the difficulty of registration due to fewer homonym points scanned on both sides by utilizing the feature of abundant three-dimensional structure information of jube crown,and finally,complete the accurate registration of jube point cloud.Neighbouring jujube branches and ground objects in the scene are proposed based on European clustering algorithm to obtain complete jujube point cloud.Three-dimensional reconstruction of jujube crown.In this paper,the crown contour and branches of jujube were reconstructed by using point cloud extracted from jujube tree,and the accuracy of reconstruction was verified by comparing crown width parameters.Fast reconstruction of jujube contour is realized by A-shape algorithm.The radius corresponding to the skeleton points and skeleton points of jujube is obtained by using level set and European clustering algorithm,and then the topological structure of the skeleton points of jujube is obtained by using the minimum spanning tree.Finally,the branches of jujube are constructed by using the generalized cylinder to complete the branch reconstruction.The accuracy of the scanning platform is verified by comparing the parameters of crown amplitude of jujube trees in North and south.The crown amplitude data obtained from point cloud contour data is compared with the manual measurement data by linear model fitting.The correlation coefficient r of the two data is 0.91,the root mean square error is 0.06,and the relative error is 4.08%.The fitting effect is better.This method has certain feasibility and practical significance.