基于双目相机的森林样地调查方法研究

Investigation Method of Forestry Plot Based on Binocular Stereo Camera

为了提高样地调查时的野外工作效率,设计了一种相片样地建立方法,以双目相机为测量工具,在样地中心上下放置双目相机,依次进行12次30°的旋转拍摄,获取12组立体相对,配合少量的现场目视检查和遮挡木补测,以立体相对前方交会作为内业处理手段,提取并纠正相片中各目标木的胸径和树心坐标,利用左右旋转角度和将树心坐标转换至同一坐标系中,完成样地各目标木的胸径提取、样木坐标提取、蓄积量计算等工作。为了验证该方法,选择了9块固定样地进行相片样地建立,分别对比相片样地与固定样地调查中提取的胸径、树心坐标、蓄积量和工作时间,其中蓄积量的平均相对误差为5.5%,最大相对误差为8.2%。

In order to improve efficiency of field operation in normal plot investigation, the photograph plot method was studied. The binocular stereo camera was chosen as the main tool. We placed the binocular stereo camera vertically in the center of plot, took twelve 30-degree-shots and got twelve groups of stereo images in turn. The field visual examination was used to cheek the shielding tree. After the supplementary surveying of the shielding tree, we used forward intersection to obtain the coordinate of homonymy points in the stereo images so as to extract the diameter and relative coordinate of the target tree. The photograph plot was then finished after all the coordinates had been transformed to the same coordinate system by the rotation angle. In order to verify the proposed method, nine fixed sample plots were chosen as examples to make a comparison between the results of photograph plot and the normal method. The results included the diameter and the coordinate of each target tree, the volume of fixed sample plot and the working time of two methods above. The results show that the average fractional error of plot volume is 5.5%, and the maximum error is 8.2%. The comparison results confirmed the feasibility of photograph plot.