地面激光雷达扫描参数与点云简化对林木参数提取的影响

Effects of terrestrial LiDAR scanning parameters and point cloud simplification on forest parameters extraction

【目的】林木参数是森林蓄积量、森林生物量估算的基础指标,传统的人工调查方式费时费力,已难以适应新形势下数字化森林资源监测技术的要求。地面激光雷达扫描技术能够获取小尺度高分辨率的林分内部结构信息,为林分环境条件下林木胸径、树高提取提供一种新的思路。【方法】以芦头实验林场杉木林样地为研究对象,针对FARO Focus 3D X330三维激光扫描仪设计了7种不同的扫描组合方式对样地进行扫描,提出象限角点云简化思路进行参数提取和精度评价,探究不同扫描组合方式对林木胸径、树高参数提取精度与效率的影响。【结果】1)当扫描分辨率为1/2、质量为4X时,胸径参数提取精度最高;当扫描分辨率为1/4、质量为4X时,树高参数提取精度最高。2)在林木参数提取结果没有显著性差异的前提下,扫描分辨率为1/4、质量为4X的扫描参数工作效率最高。3)选取同时兼顾精度和效率的1/4扫描分辨率、质量4X的扫描结果,进行象限角点云简化,简化的点云能够准确地提取出林木胸径参数。【结论】研究结果对于具有相同或相似地理条件和树种的林地选择扫描参数和点云简化方式具有重要参考价值,可以提高内业工作效率,同时也为地面激光雷达野外样地调查提供方法和技术参考。

【Objective】Forest parameters are the basic indicators for estimating forest volume and forest biomass,and the traditional manual survey method is time-consuming and laborious,and it is difficult to adapt to the requirements of digital forest resources monitoring technology under the new situation.Terrestrial LiDAR scanning technology can obtain small-scale and high-resolution internal structure information of forest stands,which provides a new idea for extracting diameter at breast height and tree height under stand environmental conditions.The existing terrestrial LiDAR scanning studies mostly focus on the extraction methods of forest parameters,but pay less attention to the combination of scanning resolution and quality,and the simplification of laser point clouds.【Method】Taking the Chinese fir forest of Lutou Experimental Forest Farm as the research object,this paper designed seven different scanning combinations for the FARO Focus 3D X3303D laser scanner to scan the sample plot,and proposed the idea of quadrant corner point cloud simplification for parameter extraction and accuracy evaluation,and then explored the influence of different scanning combinations on the accuracy and efficiency of forest diameter at breast height and tree height parameter extraction.【Result】1)When the resolution was 1/2 and the quality was 4X,the accuracy of the diameter at breast height parameter extraction was the highest;and when the resolution was 1/4 and the quality was 4X,the extraction accuracy of tree height parameters was the highest.2)Under the condition that there was no significant difference in extractied forest parameters,the scanning parameters with a quality of 4X work the most efficiently when the resolution was 1/4.3)Select scan results with a resolution of 1/4 and a quality of 4X,which took accuracy and efficiency into account,and simplified the quadrant corner point cloud.The simplified point cloud accurately extracted the parameters of the diameter at breast height of individual trees.【Conclusion】The results of this study have important reference value for the selection of scanning parameters and point cloud simplification methods for forest land with the same or similar geographical conditions and tree species,which can improve the efficiency of the data processing,and also provide a method and technical reference for the field sample survey by terrestrial LiDAR.