Digital Approach for Measuring Tree Diameters in the Amazon Forest

ABSTRACT Buttresses and other natural structures modify the shape of stems in Amazonia and change the diameter at breast height (DBH) measured at 1.3 m at ground level. The lack of adequate measurement techniques affects negatively forest dynamics analyses and biomass estimating. The study evaluated an indirect method of measuring diameters in trees with DBH > 40 cm using principles of digital photogrammetry. The results obtained with two cameras (smartphone and Sony) were compared with direct measurements using diametric tape and a ladder. The technique is adequate to measure the diameters of trees with measurement point above 2 m of ground, with a confidence interval of ±1cm. The use of photogrammetry as a supplementary tool to the diametric tape (IC ± 0.24 cm) is recommended, helping to measure trees with diameter above the reach of the technician in forest inventories.

摘要 亚马逊区域内的板状根（buttresses）及其他天然结构会改变树木茎干形态，进而干扰距地面1.3米处的胸径（diameter at breast height, DBH）测量结果。现有测量技术的不足会对森林动态分析与生物量估算产生负面影响。本研究基于数字摄影测量（digital photogrammetry）原理，针对胸径大于40厘米的树木，评估了一种间接测径方法。研究将采用智能手机与索尼（Sony）两款相机获取的测量结果，与使用测径尺及登高梯开展的直接测量结果进行对比。结果显示，该技术可有效测量测点距地面高度超过2米的树木胸径，置信区间为±1厘米。本研究建议将摄影测量技术作为测径尺的辅助工具（置信区间±0.24厘米），以辅助完成森林清查中技术人员无法直接触及的树木直径测量任务。