Underwater Stereo Mapping with Refraction Correction

This work presents the a method for underwater stereo mapping and localization for detailed inspection tasks. The method generates dense, geometrically accurate reconstructions of underwater environments by compensating for the negative effects caused by image distortions due to refraction. A refractive model of the camera and enclosure is calculated offline using calibration images and produces non-linear epipolar curves for use in stereo matching. An efficient block matching algorithm traverses the precalculated epipolar curves to find pixel correspondences and depths are calculated using pixel ray-casting. Finally the depth maps are used to perform dense simultaneous localization and mapping to generate a 3D model of the environment. The localization and mapping algorithm incorporates refraction corrected raycasting to improve map quality. The method is shown to greatly improve overall depth map quality and to generate high quality 3-D reconstructions.