Comparing Uncertainty Associated With 1-, 2-, and 3D Aerial Photogrammetry-Based Body Condition Measurements of Baleen Whales
Comparing Uncertainty Associated With 1-, 2-, and 3D Aerial Photogrammetry-Based Body Condition Measurements of Baleen Whales
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DOI：
10.3389/fmars.2021.749943
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发表时间：
2021-11-26
影响因子：
3.7
通讯作者：
Johnston, David W.
中科院分区：
文献类型：
--
作者：
Bierlich, K. C.;Hewitt, Joshua;Johnston, David W.
身体状况是动物健康的关键指标，反映了整体觅食成功，栖息地质量以及能量摄入和能量投资之间的平衡，以促进生长，维持和繁殖。最近，基于无人机的摄影测量提供了新的机会，可以在一维，二维或三维（分别为1D，2D和3D）中获得须鲸的身体状况估计-分别是单一宽度，投影背表面面积或身体体积测量。然而，迄今为止还没有研究比较这些方法之间的差异，并描述测量不确定性如何在这些维度上扩展。这种相关的不确定性可能会影响从这些测量结果中得出的推断，这可能导致对数据的误解，并且缺乏对身体状况测量结果的比较限制了研究之间结果的比较。在这里，我们开发了一个贝叶斯统计模型，使用已知大小的校准对象来预测未知大小的对象的长度和宽度测量值（例如，鲸鱼）。我们使用拟合模型来预测和比较与蓝色，座头鲸和南极小须鲸的1D，2D和3D基于摄影测量的身体状况测量相关的不确定性-三种须鲸的身体尺寸范围。该模型输出身体状况测量的后验预测分布，并允许构建最高后验密度区间以定义测量不确定性。我们发现，不确定性在多维测量中不会线性缩放，与1D相比，2D和3D不确定性分别增加了1.45和1.76倍。每个标准化的身体状况测量彼此高度相关，但二维身体面积指数（BAI）占潜在的变化沿着每个物种的身体，是最精确的身体状况度量。我们希望这项研究将作为一个指南，以帮助研究人员选择最合适的身体状况测量为他们的目的，并允许他们将摄影测量的不确定性与这些测量，这反过来又将促进跨研究的结果比较。
Body condition is a crucial and indicative measure of an animal's fitness, reflecting overall foraging success, habitat quality, and balance between energy intake and energetic investment toward growth, maintenance, and reproduction. Recently, drone-based photogrammetry has provided new opportunities to obtain body condition estimates of baleen whales in one, two or three dimensions (1D, 2D, and 3D, respectively) - a single width, a projected dorsal surface area, or a body volume measure, respectively. However, no study to date has yet compared variation among these methods and described how measurement uncertainty scales across these dimensions. This associated uncertainty may affect inference derived from these measurements, which can lead to misinterpretation of data, and lack of comparison across body condition measurements restricts comparison of results between studies. Here we develop a Bayesian statistical model using known-sized calibration objects to predict the length and width measurements of unknown-sized objects (e.g., a whale). We use the fitted model to predict and compare uncertainty associated with 1D, 2D, and 3D photogrammetry-based body condition measurements of blue, humpback, and Antarctic minke whales - three species of baleen whales with a range of body sizes. The model outputs a posterior predictive distribution of body condition measurements and allows for the construction of highest posterior density intervals to define measurement uncertainty. We find that uncertainty does not scale linearly across multi-dimensional measurements, with 2D and 3D uncertainty increasing by a factor of 1.45 and 1.76 compared to 1D, respectively. Each standardized body condition measurement is highly correlated with one another, yet 2D body area index (BAI) accounts for potential variation along the body for each species and was the most precise body condition metric. We hope this study will serve as a guide to help researchers select the most appropriate body condition measurement for their purposes and allow them to incorporate photogrammetric uncertainty associated with these measurements which, in turn, will facilitate comparison of results across studies.