Optical surveying techniques for 3D reconstruction of submerged archaelogical artefacts

Abstract

This thesis is concerned with optical surveying techniques for 3D reconstruction in underwater environment. In particular, it focuses on 3D modelling of archaeological areas, lying both in shallow and deep water. Virtual representations of archaeological sites are required by researchers in order to enhance study and preservation methodologies and also to ease promotion and dissemination. The presented work mainly follows two research lines. First, it tackles the main problems arisen for standard 3D reconstruction algorithms and procedures when applied on submarine datasets. Multi-View mapping algorithm has been investigated and enhanced in order to achieve high accuracy reconstruction of two submerged villae, despite the challenging context of Baia Archaeological Park. Then, the textured and high detailed models can be employed for different purposes; in particular, some examples of virtual exploration, simulation for device design and for intervention planning and monitoring are shown. The second research line deals with the implementation of a Simultaneous Localization and Mapping (SLAM) algorithm for Unmanned Underwater Vehicles (UUVs). Some datasets acquired by an UUV equipped with typical navigation sensors and with a stereo-camera have been processed through the implemented Extended Kalman Filter (EKF), in order to perform sensor fusion and enhance both vehicle tracking and 3D scene reconstruction. Additionally, Augmented State Kalman Filter (ASKF) has been implemented in order to exploit optical data for loop closure detection in order to reduce drift error, typical of dead-reckoning navigation.