Three-Dimensional Visual Mapping of Underwater Ship Hull Surface using View-based Piecewise-Planar Measurements

Abstract

Visual inspection of underwater ship hulls using unmanned underwater vehicles needs to be conducted at very close range to the target surface because of the limited visibility conditions in underwater environments due to light attenuation, scattering, and turbidity. These environmental challenges result in ineffective photometric and geometric information in hull surface images, and thus, the performance of conventional 3D reconstruction techniques is often not satisfactory. This paper presents a visual mapping method for 3D reconstruction of underwater ship hull surface using a monocular camera as a primary mapping sensor. The main idea of the proposed approach is to model the moderately curved hull surface as a combination of piecewise-planar panels, and to generate a global map by aligning the images in a 2D reference frame and correcting them appropriately to reflect the information of perspective projections of the 3D panels. Experimental results are shown to demonstrate the feasibility of the proposed method using a dataset obtained in a field experiment with a full-scale ship in a real sea environment.