Abstract
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.
Highlights
Low- and medium-cost camera solutions are used for a wide range of underwater applications
The contributions of this paper include the comparison of in-air and underwater camera calibration parameters of the same cameras with a specific focus on quantifying any chromatic aberration (CA)
The independent adjustment (IDP) and combined adjustment (CMB) adjustments suggest the existence of longitudinal CA
Summary
Low- and medium-cost camera solutions are used for a wide range of underwater applications. Many of those applications focus on coral reefs including habitat mapping [1], dimensional and colorimetric reconstruction [2] and fractal dimension and vector dispersion estimation [3]. The basis for the photogrammetric processing of any images (captured underwater or in-air) is usually predicated on the assumption that light rays travel in a straight line. This allows the application of the collinearity equations. Any deviation in the direction of the light ray can be modeled by introducing additional camera parameters
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
