Detecting change in coral reef 3D structure using underwater photogrammetry: critical issues and performance metrics
Detecting change in coral reef 3D structure using underwater photogrammetry: critical issues and performance metrics
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DOI：
10.1007/s12518-019-00263-w
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发表时间：
2020-04
影响因子：
2.7
通讯作者：
P. Rossi;C. Castagnetti;A. Capra;A. Brooks;F. Mancini
中科院分区：
文献类型：
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作者：
P. Rossi;C. Castagnetti;A. Capra;A. Brooks;F. Mancini
本文介绍了一项位于法属波利尼西亚Moorea的珊瑚礁斑块的多时间水下摄影测量调查，旨在检测珊瑚生长10-15毫米/年。动态结构摄影测量和水下图像可以在斑块尺度上对珊瑚礁结构复杂性和生态相关特征进行三维量化。为了保证在同一参考系统内随时间的测量的可重复性，需要高度的精度和精细的分辨率，这意味着必须有一个适当的大地测量网和采集方案。适当设计测量工具和参考点，以约束摄影测量重建。通过距离差和高差观测进行网络平差，水平和垂直分量的平均精度分别为±1.2 mm和±2.9 mm。在2017年和2018年的监测活动中，摄影测量重建的最终精度分别为1厘米和几毫米。这导致在比较中实现误差约为±1厘米。大于这个量级的坐标变化可以合理地解释为珊瑚的生长或溶解。两个后续点云的直接比较对于评估生长趋势和进行形态计量分析是有效的。为了对局部变化进行高度精确的定量评估，专家操作员可以创建和分析从点云轻松生成的特定2D轮廓。
This paper presents a multi-temporal underwater photogrammetric survey of a reef patch located in Moorea, French Polynesia, designed to detect a coral growth of 10–15 mm/year. Structure-from-Motion photogrammetry and underwater imagery allows the three-dimensional quantification of reef structural complexity and ecologically relevant characteristics at the patch scale. A high degree of accuracy and fine resolution are required in order to guarantee the repeatability of surveys over time within the same reference system, meaning a proper geodetic network and acquisition scheme are mandatory. Measuring tools and reference points were properly designed in order to constrain the photogrammetric reconstruction. The network adjustment, performed with distance and height difference observations, provided an average accuracy of ± 1.2 mm and ± 2.9 mm in the horizontal and vertical components, respectively. The final accuracies of photogrammetric reconstructions are on the order of 1 cm and few millimeters for the 2017 and 2018 monitoring campaigns, respectively. This results in realized errors in the comparison of about ± 1 cm. Coordinate variations larger than this magnitude can be reasonably interpreted as coral growth or dissolution. The direct comparison of the two subsequent point clouds is effective in order to evaluate trends in growth and perform morphometric analyses. For highly accurate quantitative assessment of local changes, an expert operator can create and analyze specific 2D profiles that are easily produced from the point clouds.