3D reconstruction of underwater scene for marine bioprospecting using remotely operated underwater vehicle (ROV)

Marine bioprospecting is the procedure of identifying the characteristics of marine organisms to develop them into commercial products. This paper proposes a 3D reconstruction algorithm to facilitate 3D visualization of underwater scene for the marine bioprospecting using remotely operated underwater vehicle (ROV). It allows to provide an operator with intuitive user interface and accordingly contribute to enhance the operability of the ROV in the bioprospecting operation. The reconstruction algorithm transforms 2D pixel coordinates of the sonar image into the corresponding 3D spatial coordinates of the scene surface by restoring the surface elevation missing in the sonar image. First, the algorithm segments the objects and shadows in the image by classifying the pixels based on the intensity value of the seafloor. Second, it computes the surface elevation on the object pixels based on their intensity values. Third, the elevation correction factor, which is derived by the ratio between height of the object and the length of the shadow, is multiplied to the surface elevation value. Finally, the 3D coordinates of the scene surfaces are reconstructed using the coordinate transformation from the image plane to the seafloor with the restored surface elevation values. The experimental results show the algorithm successfully reconstructs the surface of the reference object within an error range less than 10 % of the object dimension, and practical applicability to the marine bioprospecting operation.