基于三维点云测量个体树木疏透度的方法研究

Research on a Method for Measuring Individual Tree Optical Porosity Based on Three-dimensional Point Cloud

摘要

树木疏透度表征树木孔隙特征，研究其测量方法对于树木热舒适调节研究具有重要意义。传统树木疏透度测量方法较为烦琐，受限于摄影图像的获取难度而难以应用于单棵树木水平面疏透度测量，且测量精度易受自然光线影响。本文借助三维点云技术探索高效提取树木个体疏透度参数的技术流程。在辨析疏透度相近概念并明确本文研究对象之后，随机挑选5棵常用园林绿化树木，分别采集其点云数据和摄影图像。借助二维分箱思想和点云边界提取方法统计树木点云正投影平面剪影孔隙区域和非孔隙区域网格数量，计算基于点云的树木疏透度，并借助树木摄影图像按照传统方式计算树木疏透度作为对比参照，对点云方法进行误差检验和准确性检验，验证方法有效性。经验证，点云方法测量的疏透度结果与传统方法测量结果高度相关且接近1∶1的关系，本文提出的基于三维点云测量树木疏透度的方法具有较高的准确性，且可以成功应用于树木水平面疏透度测量。研究结果可以代替传统方法实现树木个体疏透度参数的高效提取，并成功弥补了传统方法难以测量树冠水平疏透度的问题，为精细化树木遮荫效益和热舒适调节效益评估实践奠定基础。

Abstract

Tree optical porosity is characterized by the pore structure of trees, and studying its measurement methods is crucial for research on tree thermal comfort regulation. Traditional tree optical porosity measurement methods are cumbersome, constrained by the difficulty of acquiring photographic images, making them impractical for measuring horizontal porosity of individual trees. Moreover, measurement accuracy is easily affected by natural light. This paper employs 3D point cloud technology to explore an efficient workflow for extracting individual tree canopy openness parameters. After distinguishing the similar concepts of tree optical porosity and clarifying the research objects of this paper, five commonly used garden trees in urban greening in the north and south are randomly selected, and their point cloud data and photographic images are collected respectively. By means of the 2D-binning concept and point cloud boundary extraction method, the number of grids in the pore area and non-pore area of the orthographic projection plane silhouette of tree point clouds is counted. The tree porosity based on the point cloud is calculated, and it is compared with the traditional method using tree photographic images as a reference. Then, error tests and accuracy tests are conducted on the point cloud method to validate its effectiveness. Verification demonstrates that the canopy optical porosity results measured by the point cloud method show a high correlation with those from the traditional method, with a close 1∶1 relationship. The proposed 3D point cloud-based method for measuring tree canopy openness exhibits high accuracy and can be successfully applied to horizontal canopy openness measurements. The research results can replace traditional methods for the efficient extraction of individual tree canopy openness parameters, successfully addressing the limitation of conventional approaches in measuring horizontal canopy openness. This establishes a practical foundation for refining assessments of tree shade benefits and thermal comfort regulation.

关键词

树木疏透度 / 三维点云技术 / 热舒适评估 / 二维分箱

Key words

Tree optical porosity / three-dimensional point cloud technique / thermal comfort evaluation / 2D-binning

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