基于方格网法的树冠体积测算方法

Algorithm of Crown Volume with Square Grid-based Method

摘要:

提出了一种基于方格网法测算树冠体积的方法。研究利用免棱镜全站仪获取树冠点云数据，建立树冠表面特征点的坐标方格网，根据方格网法计算土方量的原理来求算树冠体积，通过传统经典模型人工方法、三维激光量测法与本文算法，分别计算实验区域研究对象的体积，将结果进行对比分析，本研究提出的算法平均相对误差为4.13%，平均准确度为95.97%，且在置信度0.05下树冠体积的计算值与实测值之间的差异性为不显著，结果完全满足计算精度，其计算耗时只有传统人工量测法的1/3，成本为三维激光扫描的2%，降低了成本且提高了效率。

关键词:树冠体积;全站仪;点云数据;方格网法;测算方法

Abstract:

A new algorithm of crown volume based on a square grid method was presented, which was low in cost and high in efficiency and precision, and the normal errors in manual measurement of parameters can be reduced, such as total height, crown width, crown projected area, and so on. While the traditional assessments were not sufficient to provide accurate parameters owing to the irregular crown shapes, and three-dimensional laser was too expensive and fussy to afford. A numerical analysis of the proposed algorithm was presented, along with a design procedure and experimental results. Comparison of obtained results from classical methods and three-dimensional laser measurement was made. The point cloud data were acquired by non-prism total station and a coordinate grid of canopy surface was built, and then the crown volume can be computed with a square grid based method. Analysis of the parameters had been made with satisfactory precise and the results showed that the relative error of square grid method was 4.13% and the average accuracy was 95.75%. There was no significant difference between calculation value and actual measurement for crown volume under confidence level of 0.05. Moreover, compared to the traditional manual measurement, only one-third of time was consumed by square grid method, which costed 2% of those by three-dimensional laser scanning, therefore, the expenditure was extremely reduced and efficiency was increased. 

Key words:Crown volume;Total station;Point cloud data;Square grid method;Algorithm