Search Results (7)

This study presents a finite element-based numerical simulation of a shipwreck scenario at the 4th-century BC underwater archaeological site near the island of Žirje, integrating engineering analysis with archaeological interpretation. The site is notable for the wide scattering of amphorae across the seafloor. A scaled model, based on the well-documented Kyrenia shipwreck, found off the coast of Cyprus, was developed to approximate the estimated parameters of the Žirje vessel, incorporating reduced dimensions, an adjusted freeboard, and a total deadweight of approximately six tons. The finite element model of the ship, its cargo, and the seabed was developed using LS-DYNA R11.1. software. Instead of fluid modelling, the study employed explicit dynamic analysis with a rigid seabed, gravitational loading, and automatic contact to reduce computational cost. A series of parametric simulations explored the effects of roll, yaw, and varying gravitational forces on the sinking behaviour and cargo dispersion. Results indicate that only certain non-uniform sinking conditions, combined with seabed currents, accurately replicate the archaeological distribution of the amphorae. This approach underscores the value of integrating finite element analysis (FEA) with archaeological data to generate digitally supported hypotheses, demonstrating how numerical reconstruction can enhance the interpretation of complex underwater archaeological sites. Full article

Bengala, a steamer that sank in 1889 near Capo Rizzuto, Italy, was a relatively new vessel for its time, with an unusually short 18-year service life, given that steamers of the period typically operated for 30 to 40 years. Despite its brief history, SS Bengala played a significant role in the development of Italy’s young merchant navy, undergoing multiple ownership changes and serving various Italian shipping companies. Employed mainly along the route to Southeast Asia, it transported Italian migrants overseas and also participated in troop raids during the Italian military expedition to Eritrea in 1887. Despite its historical significance, no iconographic material has yet been found to depict SS Bengala, and archival research conducted in Italy and England has not uncovered any naval plans, photographs, or drawings of the ship. To overcome this gap, the authors employed new technologies and historical information to create a virtual reconstruction. This research combined archival sources with underwater surveys, including a detailed 3D survey by divers and archaeologists. Archival research, including consultation of official documents, provided critical information on the ship’s dimensions, superstructure, rigging, materials, and construction methods. The 3D modelling of the ship’s external hull, based on precise geometric data from the wreck site, offers a first step towards virtual reconstruction. The modelling is grounded in photogrammetric surveying techniques, ensuring high accuracy in the reconstruction process. The model can be used in augmented reality (AR) applications to enhance underwater exploration, allowing divers to visualise the reconstructed ship in its original environment. Additionally, it supports museum exhibits, interactive visualisations, and educational games, making it a valuable resource for engaging the public with maritime history and archaeology. Full article

Wooden ships on the shipwreck sites are usually only partially preserved, and reconstructing the original hull lines requires considerable effort. The shape of the hull has a direct effect on the ship’s capacity to carry cargo, as well as on its speed and stability. When reconstructing the hull lines, the incomplete nature of the archaeological remains results in the interpretation of the available data. The outcome, therefore, depends on the assumptions and decisions associated with the reconstruction process. This paper examines how the variation in a single parameter, namely, the beam, affects the performance of the vessel. Considering the availability of the model, the Kyrenia ship from the fourth/third century BC is used as a case study. The scope of this paper is to demonstrate and quantify the effect of beam variation on ancient ship performance, namely, the ship cargo capacity, stability, and resistance. Kyrenia ship was used as a study case based on hull lines proposed by Steffy in 1985. The aim is not to modify Steffy’s original reconstruction but to demonstrate that small deviations could significantly affect the performance of the vessel. In addition, an increase in the height of the ship’s sides is proposed as a possible solution to increase the load capacity of the ship. The opportunity to explore a whole set of trials and reconstructive variations with naval engineering software can deepen our understanding of ship performance, allowing us to improve our approach to reconstruction, too. Full article

The limited number and under-representation of side-scan sonar samples hinders the training of high-performance underwater object detection models. To address this issue, in this paper, we propose a diffusion model-based method to augment side-scan sonar image samples. First, the side-scan sonar image is transformed into Gaussian distributed random noise based on its a priori discriminant. Then, the Gaussian noise is modified step by step in the inverse process to reconstruct a new sample with the same distribution as the a priori data. To improve the sample generation speed, an accelerated encoder is introduced to reduce the model sampling time. Experiments show that our method can generate a large number of representative side-scan sonar images. The generated side-scan sonar shipwreck images are used to train an underwater shipwreck object detection model, which achieves a detection accuracy of 91.5% on a real side-scan sonar dataset. This exceeds the detection accuracy of real side-scan sonar data and validates the feasibility of the proposed method. Full article

With the increasing demand for underwater resource exploration, three-dimensional (3D) reconstruction technology is important for searching for lost underwater civilizations, underwater shipwrecks, or seabed structures. However, faced with the limitations of underwater unmanned systems in terms of energy, bandwidth, and transmission delay, 3D reconstruction technology based on video streams as direct data will not work well. We propose a terminal image processing strategy to save data transmission time and cost and to obtain 3D scene information as soon as possible. Firstly, we propose an adaptive threshold key frame extraction algorithm based on clustering, which extracts key frames from the video stream as structure from motion (SFM) image sequences. On this basis, we enhance the underwater images with sufficient and insufficient illumination to improve the image quality and obtain a better visual effect in the 3D reconstruction step. Additionally, we choose global SFM to construct the scene and propose a faster rotation averaging method, the least trimmed square rotation averaging (LTS-RA) method, based on the least trimmed squares (LTS) and L1RA methods. It is proven to reduce 19.97% of the time through experiments. Finally, our experiments demonstrate that the dense point cloud saves about 70% of the transmission cost compared to video streaming. Full article

Through the study of three wreck sites over the Methoni Bay (Greece), this article presents the benefits of spatio-temporal integration and correlation of marine geophysical data in a common three-dimensional (3D) geographical platform for analysis, and visualisation of shipwreck ruins and for interpretation of physical processes over wreck sites. The integration of 3D datasets has been proven to support identification of archaeological features over and under the seafloor, evaluation of the wreck structure state, and assessment on the wrecking event and the wreck site arrangement at that time, due to interactive cross-examination of datasets acquired in separate planes. Data synthesis is fundamental for 3D digital reconstruction of scattered and partially buried shipwreck ruins in complex geology as every dataset acts as interpretive and complimentary to each other. It is also shown that data synthesis highlights the signatures of physical processes over the wreck sites, and the interaction between the processes and the shipwrecks. The analysis of spatio-temporal, four-dimensional (4D) integrated datasets has proved to provide knowledge on the wreck site evolution through time, and highlights the disturbance of underwater archaeological resources due to human activities. The study has also shown that the creation of a shoalest depth true position bathymetric surface supports the realistic 3D wreck representation over the seafloor. Full article

The number of researchers utilising imagery for the 3D reconstruction of underwater natural (e.g., reefs) and man-made structures (e.g., shipwrecks) is increasing. Often, the same procedures and software solutions are used for processing the images as in-air without considering additional aberrations that can be caused by the change of the medium from air to water. For instance, several publications mention the presence of chromatic aberration (CA). The aim of this paper is to investigate CA effects in low-cost camera systems (several GoPro cameras) operated in an underwater environment. We found that underwater and in-air distortion profiles differed by more than 1000 times in terms of maximum displacement and in terms of curvature. Moreover, significant CA effects were found in the underwater profiles that did not exist in-air. Furthermore, the paper investigates the effect of adjustment constraints imposed on the underwater self-calibration and the reliability of the interior orientation parameters. The analysis of the precision shows that in-air RMS values are just due to random errors. In contrast, the underwater calibration RMS values are 3x-6x higher than the exterior orientation parameter (EOP) precision, so these values contain both random error and the systematic effects from the CA. The accuracy assessment shows significant differences. Full article