To assess the ability of a satellite instrument to detect submerged targets, we constructed a semi-analytical relationship to link target reflectance and the contrast threshold of the satellite instrument to visibility ranges. Using numerical simulation, we found that the contrast threshold of the satellite instrument was equal to 50 % of the residual error contained in satellite Rrs data. We evaluated our model using known sea depths of optically shallow water and found that the model produced ∼ 16 % uncertainty in retrieving the visibility range around the edge of the optically shallow water. By comparison, the contrast threshold of the human eye was more than 20 times larger than the satellite instrument contrast threshold. In addition, using a Secchi disk submerged in the shallow water, we found that the Secchi disk was invisible to the human eye when the disk was still visible to a high-quality camera handheld or mounted on an unmanned aerial vehicle. Moreover, when the image data quality was as well as MODIS instrument, we found that the maximum instrument visibility range reached 130 m in theory, which was approximately four times larger than the maximum reached by the human eye. Our findings suggest that high-quality cameras such as satellite instruments are more effective than the human eye for detecting underwater targets.

中文翻译：

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对卫星仪器能见度范围进行建模以检测水下目标


为了评估卫星仪器检测水下目标的能力，我们构建了一个半分析关系，将目标反射率和卫星仪器的对比度阈值与能见度联系起来。使用数值模拟，我们发现卫星仪器的对比度阈值等于卫星 Rrs 数据中包含的残差的 50 %。我们使用已知的光学浅水海深评估了我们的模型，发现该模型在检索光学浅水边缘周围的能见度范围时产生了 ∼ 16% 的不确定性。相比之下，人眼的对比度阈值比卫星仪器的对比度阈值大 20 倍以上。此外，使用浸没在浅水中的 Secchi 圆盘，我们发现当圆盘仍然被手持或安装在无人机上的高质量相机仍然可见时，人眼看不到 Secchi 圆盘。此外，当图像数据质量与 MODIS 仪器一样时，我们发现理论上仪器的最大能见度范围达到 130 m，大约是人眼达到的最大能见度的四倍。我们的研究结果表明，卫星仪器等高质量相机在检测水下目标方面比人眼更有效。