摘要
胸径是立木测定的基本因子,自动获取胸径数据是准确高效计算森林蓄积量和生物量的关键。以银杏Ginkgo biloba为研究对象,通过无人机获得影像数据,利用运动恢复结构(SFM)方法生成数字表面模型和正射影像图,进而提取单株银杏的树冠面积(A_c),冠幅(W_c)及树高(H)。3个参数分别与胸径(DBH)建立一元回归模型(A_c-D_(BH),W_c-D_(BH), H-D_(BH)),二元回归模型(A_c&W_c-D_(BH), A_c&H-D_(BH), W_c&H-D_(BH))和三元回归模型(A_c&W_c&H-D_(BH))。52组拟合样本的结果显示:A_c&W_c&H-D_(BH)模型的决定系数(R~2)最高为0.825 0,均方根误差(E_(RMS))最小为0.959 1。19组检测样本的结果显示:A_c&W_c&H-D_(BH)模型反演的胸径值误差率为4.20%,小于A类森林资源胸径因子允许的误差值(5%)。研究结果表明:通过无人机采集树冠面积、冠幅和树高3个参数,可计算得到较高精度的胸径值。
To efficiently calculate and predict forest stock and biomass, diameter at breast height(DBH), a basic factor of a tree, was used in a regression model. In this study, Ginkgo biloba was used as the research object.Image data was obtained with an unmanned aerial vehicle(UAV), and using the method of structure from motion(SFM), a digital surface model and an orthophoto map were generated. Next, the canopy area(A_C), crown width(W_C) and tree height(H) of G. biloba were extracted. Then, one-way regression models(A_C-D_(BH), W_CD_(BH), H-D_(BH)), binary regression models(A_C&W_C-D_(BH), A_C&H-D_(BH), W_C&H-D_(BH)), and a ternary regression model(A_C&W_C&H-D_(BH)) were established. Results of 52 groups of fitted samples showed that the A_C&W_C&H-D_(BH) model had the highest coefficient of determination(R~2= 0.825 0) and the lowest root mean square error(E_(RMS)= 0.959 1). Results of 19 groups of test samples showed that the DBHerror rate for the A_C&W_C&H-D_(BH)model was 4.20%, which was less than the allowable error value(5%) for the A-type forest resource DBHfactor. Thus,a high precision D_(BH)value could be calculated using the three parameters of canopy area, crown width, and tree height, thereby providing a new idea for automated forest resource surveying and monitoring.
引文
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