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林业科学 ›› 2018, Vol. 54 ›› Issue (7): 62-72.doi: 10.11707/j.1001-7488.20180707

• 论文与研究报告 • 上一篇    下一篇

基于机载LiDAR的单木结构参数及林分有效冠的提取

耿林, 李明泽, 范文义, 王斌   

  1. 东北林业大学林学院 哈尔滨 150040
  • 收稿日期:2017-08-16 修回日期:2018-03-21 出版日期:2018-07-25 发布日期:2018-08-11
  • 基金资助:
    国家自然科学基金项目(31470640)。

Individual Tree Structure Parameters and Effective Crown of the Stand Extraction Base on Airborn LiDAR Data

Geng Lin, Li Mingze, Fan Wenyi, Wang Bin   

  1. School of Forestry, Northeast Forestry University Harbin 150040
  • Received:2017-08-16 Revised:2018-03-21 Online:2018-07-25 Published:2018-08-11

摘要: [目的]基于机载激光雷达(LiDAR)数据提取单木树冠三维结构参数(树冠顶点位置、树高、冠幅和冠长),并在此基础上对林分有效冠进行提取,为进一步研究林分尺度上的有效冠结构及其动态提供依据,以更好掌握并改进林业经营措施。[方法]采用一定规则下的局部最大值窗口搜索树冠顶点,进行单木树冠顶点探测和单木树高提取;以树冠顶点为标记,利用标记控制分水岭分割算法提取单木冠幅;采用垂直方向点云高程检测方法获取枝下高位置,提取冠长;在标记控制分水岭分割出的树冠边界,提取树冠接触高,取平均值作为该样地的林分有效冠高。[结果]树冠分割正确率为88.5%;结合样地实测参数对提取值进行相关性分析,树高R2=0.886 2,冠幅R2=0.786 4,冠长R2=0.800 0,树高、冠幅和冠长精度分别为90.34%、86.80%和89.90%;同一林分内单木接触高相对比较稳定,对提取的林分有效冠高进行单因素方差分析,无显著差异。[结论]基于机载LiDAR数据,采用可变大小的动态窗口搜索局部最大值点,能提高单木结构参数的提取精度;利用树冠顶点标记控制分水岭算法,将高空间分辨率航片作为辅助数据,可完成较高精度的单木冠幅提取;垂直方向点云高程检测方法可提取单木冠长;LiDAR点云数据可对林分有效冠进行提取,在同一林分中,不同样本数量对接触高提取的变异性影响不大,有效冠高大致相同。机载LiDAR数据具有良好的单木树冠三维结构参数提取能力,能够满足现代林业调查对单木结构参数提取的需要,实现对林分有效冠的提取。

关键词: 机载激光雷达, 冠幅, 树高, 冠长, 林分有效冠

Abstract: [Objective] This study was performed in coniferous plantations in Mao'ershan Experiment Forest centre of Northeast Forestry University. The three-dimensional structural parameters of individual tree canopy, which included treetops position, tree height, crown size and crown height, in the study area were extracted using airborne LiDAR data. And on this basis, the effective canopy was extracted to obtain the effective canopy of the stand.[Method] In this study, we used the local maximum window with variable window sizes to search the treetops of the crown, and to identify the treetops of individual tree crown and the extraction of individual tree. Using the crown treetops mark, marker-controlled watershed method was applied to segmentation algorithm into isolating individual trees. The vertical point cloud elevation detection method was analyzed to obtain the crown base height position, then the crown height was extracted. At the border of the canopy which was divided into marker-controlled watersheds, extraction of two crowns was contact height, averaging was taken as the effective crown of the stand.[Result] The results showed that the accuracy of tree isolation was 88.5%. The correlation analysis of the extracted values was carried out by using the measured data. The R2 of tree height, crown diameter size and crown height was 0.886 2, 0.786 4 and 0.800 0, and the corresponding precision was 90.34%, 86.80%, 89.90%, respectively. The average contact height in the same forest stand was relatively stable. One-factor analysis of variance(ANOVA)was performed on the effective crown height of the extracted stands. No significant difference was found when the P-value was greater than 0.05.[Conclusion] A local maximum algorithm can be used by LiDAR to extract tree crown vertex and tree height. The variable size dynamic window is used to search for local maximum points. This method can improve the extraction accuracy of tree canopy structure parameters. Based on the tree top mark control watershed algorithm, the LiDAR data can be combined with the high spatial resolution navigation chip to complete the high-precision canopy extraction. The vertical direction detection method can extract the single crown length efficiently. In the same forest, the effective canopy of the stand is roughly the same. The airborne LiDAR can be able to extract the three-dimensional structure parameters of the single tree canopy, and can satisfy the extraction of the parameters of the single tree by the modern forestry survey and the extraction of the effective canopy of the stand.

Key words: LiDAR, crown diameter size, trees height, crown height, effective canopy of the stand

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