Walruses from space: walrus counts in simultaneous remotely piloted aircraft system versus very high‐resolution satellite imagery

IF 3.9 2区环境科学与生态学 Q1 ECOLOGY Remote Sensing in Ecology and Conservation Pub Date : 2024-05-22 DOI:10.1002/rse2.391

Hannah C. Cubaynes, Jaume Forcada, Kit M. Kovacs, Christian Lydersen, Rod Downie, Peter T. Fretwell

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Abstract

Regular counts of walruses (Odobenus rosmarus) across their pan‐Arctic range are necessary to determine accurate population trends and in turn understand how current rapid changes in their habitat, such as sea ice loss, are impacting them. However, surveying a region as vast and remote as the Arctic with vessels or aircraft is a formidable logistical challenge, limiting the frequency and spatial coverage of field surveys. An alternative methodology involving very high‐resolution (VHR) satellite imagery has proven to be a useful tool to detect walruses, but the feasibility of accurately counting individuals has not been addressed. Here, we compare walrus counts obtained from a VHR WorldView‐3 satellite image, with a simultaneous ground count obtained using a remotely piloted aircraft system (RPAS). We estimated the accuracy of the walrus counts depending on (1) the spatial resolution of the VHR satellite imagery, providing the same WorldView‐3 image to assessors at three different spatial resolutions (i.e., 50, 30 and 15 cm per pixel) and (2) the level of expertise of the assessors (experts vs. a mixed level of experience – representative of citizen scientists). This latter aspect of the study is important to the efficiency and outcomes of the global assessment programme because there are citizen science campaigns inviting the public to count walruses in VHR satellite imagery. There were 73 walruses in our RPAS ‘control’ image. Our results show that walruses were under‐counted in VHR satellite imagery at all spatial resolutions and across all levels of assessor expertise. Counts from the VHR satellite imagery with 30 cm spatial resolution were the most accurate and least variable across levels of expertise. This was a successful first attempt at validating VHR counts with near‐simultaneous, in situ, data but further assessments are required for walrus aggregations with different densities and configurations, on different substrates.

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来自太空的海象：同步遥控飞机系统与超高分辨率卫星图像中的海象数量对比

有必要对海象（Odobenus rosmarus）在泛北极地区的分布进行定期计数，以确定准确的种群趋势，进而了解当前海象栖息地的快速变化（如海冰消失）对海象的影响。然而，用船只或飞机对像北极这样广袤而偏远的地区进行调查是一项艰巨的后勤挑战，限制了实地调查的频率和空间覆盖范围。使用超高分辨率 (VHR) 卫星图像的替代方法已被证明是探测海象的有用工具，但准确计数海象个体的可行性尚未得到解决。在这里，我们比较了通过 VHR WorldView-3 卫星图像获得的海象计数和使用遥控飞机系统 (RPAS) 同步获得的地面计数。我们估计了海象计数的准确性，这取决于：(1) VHR 卫星图像的空间分辨率，以三种不同的空间分辨率（即每像素 50、30 和 15 厘米）向评估者提供相同的 WorldView-3 图像；(2) 评估者的专业知识水平（专家与混合经验水平--代表公民科学家）。后一方面的研究对全球评估计划的效率和成果非常重要，因为有公民科学活动邀请公众在 VHR 卫星图像中计数海象。我们的 RPAS "对照 "图像中有 73 只海象。我们的结果表明，在所有空间分辨率和所有评估者专业水平下，海象在 VHR 卫星图像中的计数都偏低。空间分辨率为 30 厘米的 VHR 卫星图像中的海象数量最为准确，而且不同专业水平的海象数量差异最小。这是用近乎同步的现场数据验证 VHR 计数的首次成功尝试，但还需要对不同密度和结构、不同底质的海象聚集地进行进一步评估。

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来源期刊

Remote Sensing in Ecology and Conservation Earth and Planetary Sciences-Computers in Earth Sciences

CiteScore

9.80

自引率

5.50%

发文量

审稿时长

18 weeks

期刊介绍： emote Sensing in Ecology and Conservation provides a forum for rapid, peer-reviewed publication of novel, multidisciplinary research at the interface between remote sensing science and ecology and conservation. The journal prioritizes findings that advance the scientific basis of ecology and conservation, promoting the development of remote-sensing based methods relevant to the management of land use and biological systems at all levels, from populations and species to ecosystems and biomes. The journal defines remote sensing in its broadest sense, including data acquisition by hand-held and fixed ground-based sensors, such as camera traps and acoustic recorders, and sensors on airplanes and satellites. The intended journal’s audience includes ecologists, conservation scientists, policy makers, managers of terrestrial and aquatic systems, remote sensing scientists, and students. Remote Sensing in Ecology and Conservation is a fully open access journal from Wiley and the Zoological Society of London. Remote sensing has enormous potential as to provide information on the state of, and pressures on, biological diversity and ecosystem services, at multiple spatial and temporal scales. This new publication provides a forum for multidisciplinary research in remote sensing science, ecological research and conservation science.