近景摄影测树仪的研究与开发

立木树高、胸径、任意处直径及高度是单木测量的重要因子,传统的测量方法需要多种测树工具分别进行测量,为了实现这些因子的快速非接触测量,笔者基于近景测量原理,设计了一种高速数字化、便携的近景摄影测树仪。该设备以激光尺、倾角传感器、摄像头和核心板卡等主要硬件为基础,以CCD传感器为采集信息手段。利用近景摄影技术,通过数字信号处理器及其应用系统进行图像处理,提取并存储立木的树高、胸径和任意处直径及高度等信息,实现了单次摄影测量多个测树因子的功能。试验结果表明,任意处直径测量与测树钢围尺的相对误差范围为10.193%～17.977%; 高度测量与卷尺的相对误差范围为8.763%～11.721%。树高测量与MPTS-2的相对误差为11.52%,胸径测量与测树钢围尺的相对误差为15.19%。
Forest mensuration is one of the basics in forestry science and other related fields. Tree height, diameter at breast height(DBH), diameter at arbitrary height and corresponding height are critical factors of individual tree mensuration in field investigation. These factors are measured by using multiple tools in traditional methods. Meanwhile, it is difficult to measure the diameter at arbitrary height and corresponding height when the position much higher than the height of manipulator. In order to measure these factors with the non-contact measurement method conveniently, a new close range photography instrument for tree mensuration with the characteristics of fast digitization and portability was designed based on the principle of close-range photogrammetry. The instrument consists of laser ruler, obliquity sensor, camera and the core board,and the CCD(charge coupled device)sensor acts as the tool of information acquisition. The close-range photography technology, and the digital signal processor and its application system were coupled to extract and store tree height, DBH, diameter at arbitrary height and corresponding height. Multiple tree factors could be measured through single photogrammetry. The performance of the instrument was evaluated by comparing with the hand-held total station for tree mensuration MPTS-2 designed by South Surveying and Mapping Company, and the steel enclosed ruler. The results showed that the relative error range of the diameter at arbitrary height is of 10.193%-17.977% compared with the steel enclosed ruler and that of corresponding height with the range of 8.763%-11.721% compared with tape measure. The tree height measurement error of the instrument was 11.52% relative to the MPTS-2 and the diameter error was 15.19% relative to the steel enclosed ruler respectively