基于无人机影像的天山云杉林树高提取及蓄积量的反演

【目的】提取影像高程数据建立模型反演天山云杉林分蓄积量,为天然林保护工程实施后天山云杉生态恢复与科学管理提供参考依据。【方法】以新疆天山西部巩留县恰西森林公园的天山云杉(Picea Schrenkiana var. tianshanica)为研究对象,无人机航拍影像与样地每木检尺为数据源,使用点云分类与克里金插值法提取无人机影像高程数据得到天山云杉树高,根据样地实测数据建立胸径树高模型,最终根据胸径树高模型反演天山云杉林林分蓄积量。【结果】利用无人机影像提取树高与实测树高存在显著正相关关系,提取平均精度为88.42%,建立天山云杉胸径-冠幅模型的相关系数为0.696,而胸径-树高模型的相关系数为0.730;验证胸径-树高模型,计算RMSE值为12.386,拟合效果显著。基于胸径-树高模型反演林分蓄积量精度为87.66%,与实测值比对,残差值大部分落在(-2,+2)残差区间。【结论】采用局部最大值算法对天山云杉林树高信息的提取效果较好,建立胸径-树高模型弥补了无人机不能对胸径直接测量的缺陷,进而反演天山云杉林林分蓄积量。

Height Extraction and Growing Stock Inversion of Picea schrenkiana var. tianshanica in Tianshan Mountain Based on UAV Image

【Objective】 To establish the image elevation data model for inversion of forest growing stock inversion of Picea schrenkiana var. tianshanica based on the trees in Qiaxi Forest Park in Gongliu County, western Tianshan, Xinjiang, UAV aerial image and sample ground per wooden scale as data source in the hope of providing a reference for the ecological restoration and scientific management of natural forest protection project. 【Methods】 Using point cloud classification and Kriging interpolation to extract UAV image elevation data to obtain the height of Picea schrenkiana var. tianshanica, and at the same time, the DBH tree height model was established according to the measured data of the sample land, and the forest volume of Picea schrenkiana var.tianshanica. 【Results】 There was a significant positive correlation between tree height and measured tree height extracted by UAV images. the average extraction accuracy was 88.42%. The correlation coefficient of DBH-crown width model of Picea Schrenkiana var. tianshanica was 0.696, while that of DBH-tree height model was 0.730. Verify the DBH-tree height model, the calculated RMSE value is 12.386, the fitting effect is significant. The accuracy of retrieving stand volume based on DBH-tree height model is 87.66%. Compared with the measured values, most of the residual values fall in the residual range of (- 2,+2). 【Conclusion】 The local maximum algorithm is effective in extracting tree height information of Picea Schrenkiana var. tianshanica forest. The establishment of DBH-tree height model makes up for the defect that UAV can not measure DBH directly, and then inverts the stand volume ofPicea Schrenkiana var. tianshanica forest.