Tree Vertex and Height Extraction Based on UAV Imagery and Analysis on its Influencing Factors

doi:10.13466/j.cnki.lyzygl.2019.04.016

Abstract

Abstract:

In this paper,the feasibility of using local maximum algorithm to extract tree vertices and tree height based on the canopy height model(CHM) generated by UAV imagery was discussed.In addition,the effect of resolution and window size on tree vertex extraction was also discussed.In this study,a dense conifer-broadleaf forest is used as sample plot.The SfM(Structure from Motion) algorithm was combined with the UAV images to reconstruct the research area in three dimensions,and a series of three-dimensional data such as point cloud,digital surface model(DSM),digital elevation model(DEM) and CHM were generated.Then,for different resolutions of CHM,different smoothing window size and moving window size combinations were used to extract the tree vertices and the accuracies of results were evaluated.When the CHM resolution is 0.4m,the size of smoothing window is 3×3 pixels,and the size of moving window is 3×3 pixels,the extraction accuracy of tree vertex is the highest,and the F-Measure is 77.08%.The extracted tree heights corresponding to the 37 tree vertices extracted based on the combination was compared with the tree heights measured in the field,and the R ²,RMSE,rRMSE is 0.9669,1.4114m,10.69% respectively.The results showed that UAV imagery can be used to extract tree vertices and tree heights of complex forests.Extracting the tree vertices based on the local maximum algorithm needs to determine the resolution of the CHM,the smoothing window size and the moving window size according to the actual situation to obtain the best extraction result.

Key words: unmanned aerial vehicle, tree vertex, tree height, resolution, window size

CLC Number:

S758

LIU Jiangjun, GAO Haili, FANG Luming, ZHENG Xinyu, JIANG Guangyu. Tree Vertex and Height Extraction Based on UAV Imagery and Analysis on its Influencing Factors[J]. FOREST RESOURCES WANAGEMENT, 2019, (4): 107-116.

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树高	最小值	中位数	最大值	平均数	标准差
实测树高/m	7.5	14.1	18.3	13.2	2.6330
提取树高/m	6.6	12.5	16.4	11.9	2.4402