A systematic cost-effective approach for underwater photogrammetry

Abstract

This paper presents a systematic cost-effective approach for underwater 3D photogrammetric reconstruction. Underwater 3D reconstruction is a complicated task due to limiting and varying environmental conditions such as: low light conditions, sea snow, water currents and temperature. Quay wall inspection suffers from other possible complications including the flat vertical nature of the object to be reconstructed, limited space to manoeuvre and the presence of vegetation. Commercially available underwater photogrammetry equipment is usually designed for off-shore conditions, making it too expensive for many inshore applications. Therefore, a multi-camera system consisting out of four GoPro cameras is developed and used in the context of underwater asset inspection. The system's performance in obtaining accurate 3D reconstructions is assessed using various 3D reference structures attached to a quay wall. The performance of the 4-piece camera system setup is evaluated and compared against a stereo and monocular camera setup. It was found that the 4-piece camera system is able to obtain more accurate reconstructions than stereo and monocular camera systems, especially in situations where the camera intrinsics would be unknown.