ABSTRACT Recent advances and commercialisation of unmanned aerial vehicle/red blue green (RGB) camera systems and digital photogrammetric techniques now provide a cheap and flexible alternative to higher-cost airborne platforms for routine monitoring of canopy health in timber plantations. Structure-from-Motion photogrammetry produces very dense three-dimensional (3D) point clouds which can be used to derive metrics for inventory estimation. Unmanned aerial vehicle RGB photography also captures data that can relate to tree health. In contrast to the more common use of orthorectified RGB photography to extract this spectral information, we used the software package Agisoft Photoscan to assign a simple Vegetation Index value directly to each point in the 3D point cloud. Using data acquired by a DJI Phantom 4 Pro, we present a simple processing and photogrammetric workflow solution for detecting dead and dying trees in a young Eucalyptus pellita plantation located in the provenance of Riau, Sumatra. Trees affected by the bacterial wilt Ralstonia sp. present symptoms of necrotic foliage on individual branches or the whole crown. Assigning the Visible Atmospheric Resistant Index Vegetation Index colour-coded values to individual points in the 3D point cloud significantly enhanced visualisation of necrotic foliage on individual trees in both the point cloud and the associated orthophoto compared to the RGB equivalent images. This approach could easily be operationally deployed for the rapid detection and mapping of unhealthy trees with symptoms of necrotic foliage.

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使用无人驾驶飞行器 RGB 摄影检测幼龄桉树种植园的坏死叶子 - 概念演示

摘要 无人机/红蓝绿 (RGB) 相机系统和数字摄影测量技术的最新进展和商业化现在为木材种植园冠层健康的常规监测提供了一种廉价且灵活的替代高成本机载平台的方法。Structure-from-Motion 摄影测量产生非常密集的三维 (3D) 点云，可用于导出库存估计指标。无人机 RGB 摄影还捕获与树木健康相关的数据。与更常见的使用正射校正 RGB 摄影来提取光谱信息相比，我们使用软件包 Agisoft Photoscan 直接为 3D 点云中的每个点分配一个简单的植被指数值。使用 DJI Phantom 4 Pro 采集的数据，我们提出了一个简单的处理和摄影测量工作流解决方案，用于检测位于苏门答腊廖内的一个幼龄桉树种植园中的死树和垂死的树木。受青枯病菌影响的树木 Ralstonia sp. 在个别树枝或整个树冠上出现坏死的叶子症状。与 RGB 等效图像相比，将可见大气阻力指数植被指数颜色编码值分配给 3D 点云中的各个点，显着增强了点云和相关正射影像中各个树上坏死树叶的可视化。这种方法可以很容易地在操作上部署，用于快速检测和绘制具有坏死叶子症状的不健康树木。