The number of researchers utilising imagery for the 3D reconstruction of underwater natural (e.g., reefs) and man-made structures (e.g., shipwrecks) is increasing. Often, the same procedures and software solutions are used for processing the images as in-air without considering additional aberrations that can be caused by the change of the medium from air to water. For instance, several publications mention the presence of chromatic aberration (CA). The aim of this paper is to investigate CA effects in low-cost camera systems (several GoPro cameras) operated in an underwater environment. We found that underwater and in-air distortion profiles differed by more than 1000 times in terms of maximum displacement and in terms of curvature. Moreover, significant CA effects were found in the underwater profiles that did not exist in-air. Furthermore, the paper investigates the effect of adjustment constraints imposed on the underwater self-calibration and the reliability of the interior orientation parameters. The analysis of the precision shows that in-air RMS values are just due to random errors. In contrast, the underwater calibration RMS values are 3x-6x higher than the exterior orientation parameter (EOP) precision, so these values contain both random error and the systematic effects from the CA. The accuracy assessment shows significant differences.

中文翻译：

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色差及其对水下图像处理的影响的研究

利用图像进行水下自然（例如礁石）和人造结构（例如沉船）的3D重建的研究人员的数量正在增加。通常，在空气中使用相同的程序和软件解决方案来处理图像，而无需考虑可能由于介质从空气变为水而引起的其他像差。例如，一些出版物提到了色差（CA）的存在。本文的目的是研究在水下环境中运行的低成本摄像机系统（几台GoPro摄像机）中的CA效应。我们发现，在最大位移和曲率方面，水下和空中变形曲线相差1000倍以上。此外，在空气中不存在的水下剖面中发现了显着的CA效应。此外，本文研究了调整约束对水下自校准的影响以及内部定向参数的可靠性。精度分析表明，空中RMS值仅仅是由于随机误差引起的。相比之下，水下校准RMS值比外部方向参数（EOP）精度高3x-6x，因此这些值既包含随机误差，也包含CA的系统影响。准确性评估显示出显着差异。水下校准RMS值比外部方向参数（EOP）精度高3到6倍，因此这些值既包含随机误差，也包含CA的系统影响。准确性评估显示出显着差异。水下校准RMS值比外部方向参数（EOP）精度高3到6倍，因此这些值既包含随机误差，也包含CA的系统影响。准确性评估显示出显着差异。