Abstract: This study investigates the archaeological significance and preservation state of the Lombardo, a XIX century paddle steamer closely associated with Garibaldi's Mille Expedition and now resting off the Tremiti Islands. The research aims to contextualize the vessel's historical role and to reconstruct its steam engine, paddle wheel and shipwreck dynamics, providing the first comprehensive three-dimensional documentation of the site. Underwater photogrammetry was carried out using high-resolution imaging, a dedicated geodetic network of coded markers, and Structure-from-Motion workflows to generate a scaled 3D model of the wreck. Historical and technical sources were also examined to identify the original configuration of the steam engine and paddle wheel. The results show a highly fragmented site distributed between 9 and 22 m depth, where the surviving remains corroborate historical accounts of post-wreck salvage operations and subsequent natural collapse processes. Analysis of the wreck reveals that the ship's steam engine was a Maudslay Siamese double-cylinder type, driving radial paddle wheels. The distribution of the remains also suggests that the vessel originally settled on its port side, oriented along a north–south axis. The conclusions demonstrate how integrated archaeological, geomatic, and archival methods could clarify the technical characteristics of the Lombardo and improve understanding of its post-depositional transformation, providing a robust basis for future conservation and dissemination activities.

Keywords: Italian Risorgimento | marine steam engine | maritime archaeology | shipwreck | underwater heritage | underwater photogrammetry

Abstract: Coralligenous bioconstructions are biogenic calcareous structures characterized by low accretion rate and high sensitivity to natural and anthropogenic impacts. Assessing their ecological quality and health status requires non-destructive approaches. In the project “FISR 2019_CRESCIBLUREEF”, a ROV-based coring device has been developed to collect samples while ensuring minimal impact on the ecological and structural integrity of bioconstructions and overcoming scuba diving depth and safety constraints. This study evaluates whether fragments retrieved by the device are representative of whole coralligenous build-ups (“tal-quale”) for geobiological characterization at the microscale. Representativeness is assessed through (i) preservation of microfacies textures and framework integrity in thin sections and (ii) relative abundances of skeletal and non-skeletal carbonate components quantified by point-counting. The results suggested that a coring device represents a powerful tool for obtaining representative bioconstruction samples at least in terms of the relationships and distribution between different carbonate components. This innovative approach opens new frontiers in the study of bioconstructed habitats, allowing the collection of samples suitable for qualitative and quantitative analyses while preserving ecosystem integrity. It therefore represents a step toward in sustainable marine research, with great potential for monitoring, conservation, and management of benthic habitats.

Keywords: coralligenous bioconstructions | geobiological characterization | technological innovation | underwater non-destructive sampling

Abstract: The conservation of submerged cultural heritage is increasingly prioritized, especially after the adoption of frameworks such as the 2001 UNESCO Convention on the Protection of the Underwater Cultural Heritage. The degradation of underwater archaeological sites, exacerbated by harsh marine conditions, requires effective in-situ restoration and environmental monitoring. Traditional approaches often rely on separate tools for mortar injection, water sampling, and sediment analysis, leading to logistical inefficiencies and operational challenges for divers. This study presents a novel battery-powered, multipurpose underwater tool designed to support and improve conservation work conducted by archaeologists and restorers. The device addresses multiple operational needs in a single solution, allowing underwater restorers to perform hydraulic mortar injection for structural consolidation, collect water samples for environmental monitoring, and extract sediment for archaeological analysis. The tool features a modular architecture, an ergonomic design for diver usability, a precision extrusion system for mortar delivery, and a rotating carousel with interchangeable cartridges. By combining these capabilities in one compact instrument, the device enhances the efficiency of underwater conservation and monitoring efforts. This integrated approach reduces the equipment burden, simplifies logistics, and enables faster, more flexible field interventions. Ultimately, the proposed system contributes to more sustainable and effective management of submerged cultural heritage, promoting more responsive and streamlined underwater conservation efforts.

Keywords: Product design | Underwater cultural heritage | Underwater injector device | Underwater sampling device

Abstract: The development of multi-sensor perception systems is essential to support advanced underwater robotic operations such as inspection, mapping, and manipulation, typically carried out with Remotely Operated Vehicles (ROVs). However, field testing is often costly, logistically demanding, and constrained by safety and accessibility issues. This paper presents a flexible virtual testbed for the development and validation of perception pipelines in ROV-based missions. The framework integrates Unity game engine, for high-fidelity 3D simulation, with Robot Operating System 2 (ROS2), for real-time sensor processing, robotic control, and data exchange. The testbed provides a modular emulation of ROV architectures, integrating digital vehicle replicas, configurable underwater scenes, and simulated sensors such as stereo vision, forward-looking sonar, and inertial units. This setup enables the generation of synthetic but physically consistent data streams, including depth maps, acoustic imagery, and fused spatial reconstructions. An operator console developed in Unity integrates multiple Augmented Reality (AR) strategies to enhance situational awareness and manipulation accuracy. The proposed virtual testbed offers a cost-effective and flexible environment for iterative development, debugging, and operator training. It provides a valuable tool for accelerating the design and integration of perception systems in underwater robotics, especially in scenarios where field trials are impractical or high risk.

Keywords: Augmented Reality Visualization | Multi-Sensor Perception | Underwater Manipulation | Underwater Robotics

Abstract: Underwater robotic manipulation relies on visual feedback and experience, making precision challenging, especially in underwater cultural heritage (UCH). Errors in distance estimation risk collisions or improper grasping, endangering fragile artifacts. To overcome these challenges, operators should be equipped with advanced tools and sensors that enhance their perception and interaction, enabling more precise and controlled manipulation in complex underwater environments. To this end, the paper introduces a novel framework designed to improve environmental perception during underwater manipulation operations by integrating stereo vision and acoustic imaging sensors. Unlike traditional approaches, the proposed framework is applicable in both simulated and real-world environments, providing a versatile tool for underwater robotic applications. The core of the proposed framework consists of a simulation environment built on Unity and ROS2, replicating a system that includes a Remotely Operated Vehicle (ROV) equipped with a robotic manipulator, a stereo camera, and a forward-looking sonar. Preliminary results on stereovision and acoustic imaging simulations demonstrate how the integration of these sensing modalities improves environmental perception.

Keywords: Augmented reality | Marine robotics | Robot operating system | Underwater cultural heritage | Underwater manipulation

Abstract: Monitoring marine environments is essential for understanding ecological dynamics and preserving underwater sites of scientific and cultural interest. While autonomous robotic systems can cover large areas and collect high-quality water data, scientific divers remain indispensable for survey operations due to their direct observations and selective sampling. However, underwater navigation presents significant challenges for researchers, including poor visibility, marine currents, and the absence of GNSS signals. To address these challenges, this study proposes the conceptual design of a motorized smart buoy capable of autonomous environmental monitoring and providing operational support to divers. The system integrates a suite of sensors for real-time measurement of physicochemical water parameters, a GNSS module for surface localization, and an acoustic positioning system to enhance underwater navigation. This system determines the diver's position by emitting and receiving acoustic signals. Once the position is calculated, the information is transmitted directly to the diver's tablet, enabling real-time awareness of their location, improving navigational safety, and allowing the collection of georeferenced data for more accurate environmental analysis. Furthermore, the implementation of Deep Reinforcement Learning (DRL) algorithms has been considered to optimize the trajectory of the smart buoy in dynamic marine environments, enhancing energy efficiency and monitoring accuracy. The proposed system represents a significant advancement in marine ecosystem monitoring, combining operational autonomy with adaptability to diverse application scenarios.

Keywords: Deep Reinforcement Learning (DRL) | Diver support | Marine monitoring | Smart buoy

Abstract: This paper, in the frame of the Tectonic project (TEchnological Consortium TO develop sustaiNabIlity of underwater Cultural heritage), presents recent results obtained from the work on the shipwreck of the 19th Century schooner Emma, one of the selected submerged archaeological pilot sites. The wreck of Emma is located in Chubut province, Patagonia, Argentina. The main task consisted of the development of a 3D photogrammetric model to be integrated into a virtual reality (VR) end product. The technique employed in the process is described, noting the necessary adjustments required for its application in an underwater environment. Finally, the potential of this type of technique is discussed as a means of promoting tourism as well as underwater heritage management and protection, particularly important in the context of the characteristics of the remote Patagonian region.

Keywords: Patagonia | Photogrammetry | Shipwrecks | Underwater cultural heritage | Virtual reality

Abstract: Seabed mapping represents a very useful tool for seascape characterization and benthic habitat study and requires advanced technologies for acquiring, processing, and interpreting remote data. Particularly, acoustic instruments, such as high-resolution swath bathymetry sounders (i.e., multibeam echosounder: MBES), allow us to recognize, identify, and map the extension of benthic habitats without applying invasive mechanical procedures. Bathymetry and backscatter (BS) data are crucial to perform modern habitat mapping. Although the acquisition and processing of bathymetric data follow standardized procedure (e.g., Hydrographic Organization guidelines), and recent studies have proposed recommendations for backscatter acquisition and processing, a broadly validated methodological approach, integrating geomorphometric analysis for benthic habitat mapping, is still lacking. In this work, a new approach for benthic habitat mapping, with a focus on coralligenous bioconstructions, was developed using the open-source software QGIS. This methodology, tested within the Isola Capo Rizzuto Marine Protected Area (Calabria, Italy), is designed to be freely reproducible by researchers working in the field of marine ecosystem monitoring and conservation. Through the proposed mapping procedure, it is possible to (i) identify benthic habitats in selected study areas by combining bathymetry and BS data with geomorphological indices performed in QGIS and (ii) quantitatively define the 2D and 3D distribution of coralligenous bioconstructions in terms of surface covered, thickness, and volume. Moreover, the statistical analysis of quantitative morphometric data allowed for comparison of geometric characteristics of different coralligenous morphotypes. The obtained results, combined with improvement of minimally invasive sampling and geobiological–geochemical characterization, can contribute to the development of protocols aimed at monitoring marine bioconstructed ecosystems, many of which are protected by national and international regulations due to their importance for Mediterranean biodiversity preservation, and plan actions for their protection and persistence.

Abstract: Underwater Cultural Heritage (UCH) sites offer unique opportunities for archaeological exploration and cultural tourism but remain difficult to interpret due to the environmental constraints of the underwater setting. This paper introduces an integrated Underwater Augmented Reality (UWAR) system designed to support real-Time, site-specific interpretation for recreational divers. The approach combines opto-Acoustic 3D reconstruction with thematic annotation and portable AR delivery. A high-resolution, georeferenced 3D model of the site is generated by fusing multibeam sonar and underwater photogrammetry data. This model provides the spatial framework for distributing interpretive content through georeferenced Points of Interest (POIs), including descriptive texts, images, and 3D reconstructions. The system architecture includes a smart buoy equipped with USBL and GNSS positioning systems and an underwater mobile device for AR visualization. This setup enables real-Time localization and contextual content delivery without the need for permanent infrastructure. The presented UWAR system aims to improve site readability, promote active learning and support sustainable cultural engagement, offering a scalable model for heritage interpretation in underwater environments.

Keywords: Smart Buoy | Underwater 3D Reconstruction | Underwater Augmented Reality (UWAR) | Underwater Cultural Heritage (UCH) | Underwater Navigation

Abstract: In the integration of structured light systems (SLSs) into automotive manufacturing pipelines, achieving reliable 3D reconstruction under industrial conditions remains a critical challenge. Factors such as environmental variability, surface reflectivity, and optical configuration often compromise dimensional accuracy and point cloud quality, limiting the deployment of SLSs for inspection tasks. This paper presents a practical metric-based methodology for evaluating the dimensional accuracy and point cloud quality of SLSs targeted at automotive inspection applications. Unlike existing approaches focused primarily on theoretical or hardware-specific parameters, the proposed methodology considers all phases of the acquisition–reconstruction pipeline, including calibration, environmental variability, and image enhancement strategies, to practically guide engineers step-by-step in adapting SLSs to real-world operational constraints. The methodology was experimentally validated through a case study in an automotive production setting, where it enabled the detection of reconstruction biases caused by surface reflectivity and viewing angle. It also demonstrated the ability to quantify improvements obtained through image enhancement algorithms. These results confirm the methodology's capacity to expose critical performance trade-offs and guide optimization choices in practical inspection scenarios. By offering a repeatable and application-oriented evaluation framework, the methodology supports the robust integration of digital vision systems in industrial workflows, facilitating more informed decisions for system designers, process engineers, and quality control professionals.

Keywords: 3D reconstruction | accuracy evaluation | image enhancement | manufacturing inspection | point cloud analysis | structured light system

Abstract: Ocean exploration and inspection missions involving underwater robotic systems have gained increasing popularity in various domains such as marine science, archaeology, and defense in recent years. However, deploying vessels and robotic solutions for such research activities entails significant costs for acquisition and maintenance. This is primarily due to the logistical challenges involved in transporting equipment between locations, which necessitates a substantial financial investment, in addition to expenses associated with crew and research personnel. Effective planning of survey campaigns is crucial to avoid costly missteps arising from poor organization. It ensures that expenditures are justified and that objectives are achieved without unnecessary setbacks or errors. In this context, the utilization of simulation methodologies adds invaluable value in mitigating costs and exploring various solutions before the mission is carried out in the real world. Their utility extends beyond the examination of specific sensors or setups; they are also a valuable tool for planning different campaigns with different mission objectives. In this paper, a simulation framework that integrates an Autonomous Underwater Vehicle with a Multibeam Echo Sounder as the perception sensor is presented. The objective is to streamline acoustic survey mission planning and generate synthetic acoustic image data incorporating the modeling of typical error sources, simplifying the evaluation of output data for real applications.

Keywords: Acoustic Imaging | AUV | Robot Operating System | Simulation | Underwater Robotics | Unity3D

Abstract: With increasing threats to marine ecosystems, it has become critical to develop innovative and versatile tools to monitor and protect them. In this field, Unmanned Underwater Vehicles (UUVs) have emerged as indispensable systems due to their ability to operate in extreme and inaccessible environments. Recent technological advances have led to the development of increasingly compact and modular UUVs, improving their portability, logistical efficiency and versatility. These systems support the integration of advanced payloads with specialized sensors for specific missions, providing customizable and scalable solutions. This capability, combined with an auxiliary control system which exploits the frontseat/backseat paradigm, offers promising solutions for UUV customization and scalability. In this context, the paper presents a Backseat control system developed on the Robot Operating System (ROS) platform, designed to add new operational capabilities of UUVs with limited native equipment. The system enables the execution of complex Backseat monitoring operations at different maneuvers. Integrated into a navigation payload, the Backseat system autonomously handles guidance, navigation and control tasks. The proposed scalable and modular architecture supports diverse sensors and adaptability to various UUV and (Unmanned Surface Vessel) USV models too. Validation, conducted through experiments carried out in a simulated environment, demonstrates improvements in navigation accuracy and operational efficiency.

Keywords: Backseat Driver | Hardware in the Loop | SDG14 | Unmanned Marine Vehicles | Unmanned Underwater Vehicles

Abstract: Performing precise underwater manipulation is a challenging task, especially when applied to the field of underwater cultural heritage (UCH). In fact, errors in measuring the distance between a predefined target and the manipulator's end-effector can lead to significant issues, such as collisions or challenges in grasping objects. Therefore, there is a need to equip operators with tools that enhance their visualization and interaction capabilities, enabling more precise underwater manipulation. To this end, the paper introduces a novel simulation-based approach to increase environmental perception during underwater manipulation operations based on the adoption of stereo vision and acoustic imaging sensors. Specifically, the paper presents the software architecture of an underwater simulator that leverages a graphics engine to replicate a system comprising a Remotely Operated Vehicle (ROV) equipped with a robotic manipulator, stereo camera, and forward-looking sonar. The proposed simulation framework leverages both the Unity engine and ROS2 to enhance underwater robotic simulations. This paper presents preliminary results on stereovision and acoustic simulation, demonstrating how the integration of these sensing modalities improves environmental perception during underwater manipulation tasks.

Keywords: Augmented Reality | Marine Robotics | Robot Operating System 2 (ROS2) | SDG14 | Underwater manipulation

Abstract: 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.

Keywords: 3D reconstruction | historic iron ship | maritime archaeology | shipwreck | steam-powered vessel and steamer | underwater heritage | underwater photogrammetry

Abstract: A submerged elevation located off the coast of Le Castella, a small village on the Ionian Coast of Calabria (Italy) populated for thousands of years that features notable archaeological remains from the Great Greece (Magna Graecia) and the Middle Ages, was investigated through in-depth, multidisciplinary, geoarchaeological research. This submarine elevation, once aligned with the marine terrace MIS 3 of Le Castella and still completely emerged between 10 and 8 ka years ago, slowly sank due to erosion and local tectonic-structural subsidence and was also favoured by a submerged normal fault that cuts the terrace in two. The dismantling and sinking of this part of the marine terrace has significantly changed the Late Holocene shorelines, with notable consequences on a topographic and archaeological level. In fact, one of the consequences of the sinking of this ancient promontory was the disappearance of two small islands that were reported to be right in front of Le Castella by numerous historical and cartographic sources. In the last decades, there has been a scientific debate over the existence of these islets, but no convincing evidence has been found about their actual presence up until now. This research, funded by the Marine Protected Area “Capo Rizzuto”, was conducted by means of underwater archaeological and geological surveys, geophysical seabed mapping systems, and both direct and instrumental optical surveys made with an Autonomous Surface Vehicle. The outcomes allow us to confirm the presence of these two partially emerged rock bodies up to half a millennium ago. In addition, the presence of anthropogenic extrabasinal materials in a marine area corresponding to one of the highest points of the submerged elevation allows us to define the exact position of one of the two islets. These archaeological findings have been subject, for the first time ever, to a thorough topographical and architectural analysis, then compared with other near and very similar submerged structures. On the basis of these comparisons, the findings should be attributed to the Byzantine Age or, at most, to the Middle Ages. In-depth archival research on portolan charts and navigation maps, in many cases unpublished and dating from the Middle Ages to the early 18th century, supports the results of our marine investigations from a historical point of view.

Keywords: Calabria | coastal geoarchaeology | coastline change | coastline erosion | Ionian Sea | Late Holocene | marine geology | marine geophysical investigations | Marine Protected Area of Capo Rizzuto | maritime and underwater archaeology | underwater 3D surveying | underwater acoustics

Abstract: Survey missions in the underwater environment are key activities in several application fields, but the physical properties of such a harsh environment make it challenging for both navigation and data collection. In particular, in the field of underwater photogrammetry, optical sensors are mainly installed on remotely operated vehicles (ROVs). The maneuvering is performed remotely by expert pilots who can only rely on bidimensional visual feedback from one or more camera streams. Additional navigation data can aid pilots in assessing if the mission meets the requirements while undergoing it. To this end, the paper presents a SLAM-based solution that can be used to compute parameters in support of ROV pilots during photogrammetric surveys, when a stereo-camera is equipped. In order to assess the performance of the proposed solution, different tests were conducted. These tests involved comparing the parameters derived from SLAM with the data computed by the navigation system of a professional-grade ROV. The focus of this comparison was on three key parameters: position, velocity, and distance from the target.

Keywords: Multi-camera System | Underwater 3D Reconstruction | Underwater Photogrammetry | Underwater SLAM | Underwater Survey

Abstract: The development of an Autonomous Underwater Vehicle (AUV) is driven by careful design choices in order to obtain the best trade-off between mission performance and cost. Currently, several companies provide off-the-shelf solutions for a wide variety of operational scenarios offering highly modular systems. This allows users to customize the AUV integrating custom payloads tailored for specific applications. The factory customization has a strong impact on time and resources due to significant precautions to be taken. In particular, some design constraints must be respected for the mechanical integration ensuring, at the same time, the overall neutral buoyancy of the module to preserve the final trim of the AUV. Therefore, without a careful approach during the design phase, the risk of impairing the integrity and operation of the AUV could be high. This paper describes a design methodology for the proper development of custom payloads aimed to be integrated in AUVs. The proposed methodology has been applied in the manufacturing of a custom payload that has been integrated in the AUV X-300 of Graal Tech s.r.l. The methodology results as a useful tool for AUVs customization by providing detailed guidelines for the development of specific payloads for a wide range of applications.

Keywords: Autonomous Underwater Vehicle | Balance Identification | Modular Payload Design | Shape Optimization

Abstract: The global economy heavily relies on maritime commerce, commonly known as the “Blue Economy,” which involves the transportation of raw materials and products via maritime traffic and the utilization of marine resources, including oil, gas, and underwater mines. The importance of various infrastructures linked to the sea, such as fish farms, pipelines, underwater power and data cables, cannot be overstated as they have significant impacts on both local and global economies. Therefore, safeguarding these infrastructures against both symmetric and asymmetric threats is crucial to prevent disruptions to vital services and avoid negative impacts on the economy and quality of life. This book chapter presents an underwater access control system designed to monitor and prevent unauthorized access to port areas from the seaside to safeguard maritime infrastructures. The system consists of acoustic and magnetic barriers connected to a wireless communication network that can collect and transmit data to the infrastructure control centre. The system provides robust, dependable, and secure solutions for near real-time data transfer, enabling continuous monitoring and prompt response to potential threats. This chapter provides a detailed description of the system architecture and its primary components, focusing on the technological aspects and innovative solutions used to meet the proposed requirements.

Abstract: The paper presents the development of a Virtual Reality (VR) application to perform dives in the Christoforos Shipwreck. The huge wreck lies in the Panormos Bay of Skopelos island (Greece) at a depth of 45 meters. Based on a well-known methodology designed for ancient shipwrecks, the 3D reconstruction of the underwater site has been carried out by adjusting the workflow to survey modern shipwrecks. In particular, the methodology, based on photogrammetry, is capable to provide a highly detailed 3D reconstruction of the shipwreck in a few dives, considering issues like working depth, elevations, and thin elements modelling. Moreover, the paper describes the optimization of the 3D model and the software to be executed in low-performance Head Mounted Display (HMD) devices. The resulting VR application, realized for touristic purposes, recreates the exact ambient conditions inside and outside the water simulating the flora and fauna of the place, the coastline, allowing users to live a recreational and educational experience by virtual diving in the underwater site.

Keywords: computer graphics technologies | cultural heritage | modern shipwreck | underwater photogrammetry | virtual reality

Abstract: The Marine Strategy Framework Directive (MSFD, 2008/56/EC) was adopted to achieve a Good Environmental Status (GES) in the EU's marine waters and to protect resources and ecosystem services, including the deep-sea waters and seafloor. The deep sea (below 200 m) is the largest biome on Earth, and its biodiversity plays a key role, despite being strongly threatened by several anthropogenic stressors, potentially affecting some ecosystem functions. Among the main deep-sea structuring species, the habitat-forming cold-water corals (CWCs) are known to form Vulnerable Marine Ecosystems (VMEs). In the Mediterranean Sea, in the last two decades, a significant effort has been devoted to unveiling the distribution, extension and ecological role of scleractinian CWCs (Madrepora oculata and Desmophyllum pertusum), but quantitative data on their conservation status are very limited. Because of their ecological importance and vulnerability, Italy has extended the implementation of the MSFD to the deep sea, carrying out specific monitoring programmes on these scleractinian CWCs. In this regard, this study established, for the first time, an extensive standardized baseline for national monitoring programmes focusing on two recently discovered upper bathyal areas dominated by scleractinian CWCs (Dohrn Canyon and Corsica Channel). The goal was to evaluate the ecological status of the bathyal biogenic reefs using traditional diversity and impact variables as well as the innovative photogrammetry tool. In both areas, the investigations have increased the knowledge about the extent of the habitat and new CWC assemblages in good health conditions were discovered. The pressure extent is limited with respect to the total extent of the CWC habitat, accounting for approximately 32% and 63% of the fishing-related items entangled on structuring species. The photogrammetric approach showed a deviation of about 33% in the measurement of the population size structures. Moreover, the use of a standardized operative protocol has been proposed to obtain reliable, coherent, and comparable data for future monitoring activities. This approach improved scientific knowledge for the two studied areas and it is pivotal in defining long-term monitoring activities useful to assess the effectiveness of specific protection measures, for these VMEs

Keywords: Cold-water corals | Fishing impact | Marine strategy framework directive (MSDF) | Mediterranean sea | Photogrammetry | ROV-Imaging

Abstract: Editorial - [No abstract available]

Abstract: The documentation, conservation, and preservation of underwater archaeological sites is conventionally performed by divers in shallow waters. However, when dealing with significant depths, the sites can be inaccessible for humans, presenting significant challenges and risks, making these activities hazardous. Recently, the use of robotic platform such as remotely operated vehicles (ROVs) allows to overcome the difficulty of such a harsh environment. Nevertheless, professional-grade ROVs employed for this purpose are expensive and specifically designed with integrated advanced sensor systems for data acquisition and navigation. In the context of the MSCA-RISE H2020 Technological Consortium TO develop sustainability of underwater Cultural heritage (TECTONIC) project, a solution consisting of an optical payload and an acoustic localization system for low-cost ROV, was defined in order to support ROV pilots during documentation and monitoring activities. The project aims to preserve underwater cultural heritage (UCH) encompassing the selection of a commercially available ROV and the definition of a customized hardware/software (HW/SW) architecture. After market research, a suitable commercial off-the-shelf (COTS) low-cost ROV was defined and used as the foundation for integration. Mechanical, electric, and data interface modules were designed to seamlessly integrate and manage the sensor suite. The results of the integration demonstrate the potential of the chosen algorithms and the sensor suite for improved navigation and data collection in challenging underwater environments, where high-grade and expensive sensors are not available, thereby making more accessible the field of underwater survey missions.

Keywords: Underwater 3D Reconstruction | Underwater Cultural Heritage (UCH) | Underwater Localization | Underwater Mapping | Underwater Survey

Abstract: As one of the most promising technologies for next-generation mobile platforms, Augmented Reality (AR) has the potential to radically change the way users interact with real environments enriched with various digital information. To achieve this potential, it is of fundamental importance to track and maintain accurate registration between real and computer-generated objects. Thus, it is crucially important to assess tracking capabilities. In this paper, we present a benchmark evaluation of the tracking performances of some of the most popular AR handheld devices, which can be regarded as a representative set of devices for sale in the global market. In particular, eight different next-gen devices including smartphones and tablets were considered. Experiments were conducted in a laboratory by adopting an external tracking system. The experimental methodology consisted of three main stages: calibration, data acquisition, and data evaluation. The results of the experimentation showed that the selected devices, in combination with the AR SDKs, have different tracking performances depending on the covered trajectory.

Keywords: Apple ARKit | benchmarking | Google ARCore | mobile augmented reality | simultaneous localization and mapping (SLAM) | tracking accuracy

Abstract: Underwater photogrammetry provides a means of generating high-resolution products such as dense point clouds, 3D models, and orthomosaics with centimetric scale resolutions. Underwater photogrammetric models can be used to monitor the growth and expansion of benthic communities, including the assessment of the conservation status of seagrass beds and their change over time (time lapse micro-bathymetry) with OBIA classifications (Object-Based Image Analysis). However, one of the most complex aspects of underwater photogrammetry is the accuracy of the 3D models for both the horizontal and vertical components used to estimate the surfaces and volumes of biomass. In this study, a photogrammetry-based micro-bathymetry approach was applied to monitor Posidonia oceanica restoration actions. A procedure for rectifying both the horizontal and vertical elevation data was developed using soundings from high-resolution multibeam bathymetry. Furthermore, a 3D trilateration technique was also tested to collect Ground Control Points (GCPs) together with reference scale bars, both used to estimate the accuracy of the models and orthomosaics. The root mean square error (RMSE) value obtained for the horizontal planimetric measurements was 0.05 m, while the RMSE value for the depth was 0.11 m. Underwater photogrammetry, if properly applied, can provide very high-resolution and accurate models for monitoring seagrass restoration actions for ecological recovery and can be useful for other research purposes in geological and environmental monitoring.

Keywords: bathymetry | habitat restoration | monitoring | multibeam | Posidonia oceanica | Structure from Motion | underwater photogrammetry

Abstract: The paper presents the development of a Virtual Reality application to perform dives in the Christoforos Shipwreck. The huge wreck lies in the Panormos Bay of the Skopelos island (Greece) at a depth of 45 meters. Based on a well-known methodology designed for ancient shipwrecks, the 3D reconstruction of the underwater site has been carried out by adjusting the workflow to survey modern shipwrecks. In particular, the methodology, based on photogrammetry, is capable to provide a highly detailed 3D reconstruction of the shipwreck in few dives, considering issues like working depth, elevations, and thin elements modelling. Moreover, the paper describes the optimization of the 3D model and the software to be executed in low-performance HMD devices. The resulting Virtual Reality (VR) application, realized for touristic purposes, recreates the exact ambient conditions inside and outside the water simulating the flora and fauna of the place, the coastline, allowing users to live a recreational and educational experience by virtual diving in the underwater site.

Keywords: 3D modeling | History | Image reconstruction | Ships | Three dimensional computer graphics

Abstract: Among the activities planned for the MUSAS Project, the digital reconstruction of the underwater sites constitutes a particular challenge, requiring strong cooperation between archaeologists and technicians. The case of the Villa dei Pisoni in Baiae, one of the richest in the Phlaegrean territory, is particularly interesting: the architectural remains, already documented in the 1980s and now inserted in one of the diving spots of the Underwater Park of Baiae, are disseminated on a huge surface, including quays, thermal complexes, a fishpond, and a large, luxurious viridarium. The effort required for the digital reconstruction of the ancient villa improved the previous knowledge and the lack of documentation even in a well-known site. In this paper, we will retrace the long path from the 3D reconstruction of the archaeological remains to the virtual architectural model of the villa, the numerous challenges, doubts, and uncertainties in the creation of the original spaces, and the support offered by the ancient sources, both literary and iconographic, in solving archaeological problems.

Keywords: 3D reconstruction | Baiae | Submerged sites | Underwater cultural heritage | Villae maritimae

Abstract: In recent years, the development in digital technologies such as Augmented Reality (AR) and Virtual Reality (VR) has evolved rapidly. These technologies are currently in the process of creating driving change in the Cultural and Creative Industries (CCIs), representing innovative means to share information, facilitating access and increasing the value and public awareness on Cultural and Natural Heritage. This is particularly relevant for underwater environments, where the most interesting cultural and naturalistic sites are accessible only to scuba divers, or not accessible at all, due to depth and/or environmental constraints. In addition, in underwater sites, guided diving tours are carried out by professionals that usually describe the area to be visited during the predive briefings; such step is needed due to the impossibility of underwater verbal communication without dedicated equipment, a practice very rarely adopted for recreational diving. So, these difficulties make it almost impossible to replicate under the sea, the guided tour approach that is usually offered in on‐land museums. Considering such limitations, several technological applications are emerging to increase the accessibility underwater and enrich users' experience both for divers and nondivers. This work aims to identify the potential of underwater sites (either cultural or natural) to support the development of sustainable tourism (economic, environmental, cultural and social) in the Mediterranean. Moreover, it focuses on supplying local/regional authorities and stakeholders with a multidisciplinary plan for managing Underwater Museums and Knowledge Centres, by promoting innovation in the diving industry and improving users'/tourists' experience through value‐added services and cutting‐edge technologies.

Keywords: Diving tourism | Sustainable tourism | Underwater cultural heritage | Virtual diving

Abstract: In this study, we present a framework for seagrass habitat mapping in shallow (5-50 m) and very shallow water (0-5 m) by combining acoustic, optical data and Object-based Image classification. The combination of satellite multispectral images-acquired from2017 to 2019, together with Unmanned Aerial Vehicle (UAV) photomosaic maps, high-resolution multibeam bathymetry/backscatter and underwater photogrammetry data, provided insights on the short-term characterization and distribution of Posidonia oceanica (L.) Delile, 1813 meadows in the Calabrian Tyrrhenian Sea. We used a supervised Object-based Image Analysis (OBIA) processing and classification technique to create a high-resolution thematic distribution map of P. oceanica meadows from multibeam bathymetry, backscatter data, drone photogrammetry and multispectral images that can be used as a model for classification of marine and coastal areas. As a part of this work, within the SIC CARLIT project, a field application was carried out in a Site of Community Importance (SCI) on Cirella Island in Calabria (Italy); different multiscale mapping techniques have been performed and integrated: the optical and acoustic data were processed and classified by different OBIA algorithms, i.e., k-Nearest Neighbors' algorithm (k-NN), Random Tree algorithm (RT) and Decision Tree algorithm (DT). These acoustic and optical data combinations were shown to be a reliable tool to obtain high-resolution thematic maps for the preliminary characterization of seagrass habitats. These thematic maps can be used for time-lapse comparisons aimed to quantify changes in seabed coverage, such as those caused by anthropogenic impacts (e.g., trawl fishing activities and boat anchoring) to assess the blue carbon sinks and might be useful for future seagrass habitats conservation strategies.

Keywords: Habitat mapping | Mediterranean sea | Multibeam bathymetry | Object-based image analysis (OBIA) | Pléiades-HR satellite images | Seafloor mapping | Seagrass | Tyrrhenian sea | UAV

Abstract: Documentation and conservation of underwater cultural heritage (UCH) are crucial to preserving humankind's history and traditions, safeguarding tangible testimonies of past human life while ensuring its accessibility to future generations. The TECTONIC (Technological Consortium TO develop sustainability of underwater Cultural Heritage) project is promoting an intersectoral collaboration between academic and non-academic professionals (i.e., archaeologists, conservators, geologists, engineers, etc.) working on different topics related to UCHs, to find solutions to the issues still existing in the field. The overall aim is the exchange of skills for the improvement and assessment of innovative materials and techniques to develop solutions and marketable products for the conservation and management of the UCH, sustainably. To achieve its overall aim, TECTONIC is undertaking activities driven by the following objectives: (a) the study, documentation, and mapping of selected UCHs; (b) the creation of decision-support tools for UCH risk assessment in a changing environment; (c) the initiation of conservation studies and protocols for conservation activities; (d) the development of open and low-cost robotic solutions for the inspection of UCH; and (e) the raising of public awareness and knowledge about UCH. All the objectives are devoted to stimulating new sustainable ideas that would bring the growth of cultural tourism and the development of new marketable products by capitalizing on the research results.

Keywords: Archaeology | Materials | Protection | Sustainability | Tourism | Underwater cultural heritage (UCH); 3D

Abstract: The paper presents the MOLUX project which aims to design and develop a system capable of supporting the underwater operators by means of innovative technologies for the diagnosis, recovery, management, conservation, and valorization of the archaeological and naturalistic assets in the marine environment. This system allows to increase the efficiency and the safety of the operations carried out in the underwater environment thanks to its capabilities: to make the diver aware of his/her position; to acquire geolocated data (images, videos, notes, environmental parameters); to optimize and monitor the planned dive route.

Keywords: Autonomous surface vehicle | Diver operation support | Monitoring | Underwater localization | Underwater tablet

Abstract: The Mediterranean Sea has a vast maritime heritage which exploitation is made difficult because of the many limitations imposed by the submerged environment. Archaeological diving tours, in fact, suffer from the impossibility to provide underwater an exhaustive explanation of the submerged remains. Furthermore, low visibility conditions, due to water turbidity and biological colonization, sometimes make very confusing for tourists to find their way around in the underwater archaeological site. To this end, the paper investigates the feasibility and potentials of the underwater Augmented Reality (UWAR) technologies developed in the iMARECulture project for improving the experience of the divers that visit the Underwater Archaeological Park of Baiae (Naples). In particular, the paper presents two UWAR technologies that adopt hybrid tracking techniques to perform an augmented visualization of the actual conditions and of a hypothetical 3D reconstruction of the archaeological remains as appeared in the past. The first one integrates a marker-based tracking with inertial sensors, while the second one adopts a markerless approach that integrates acoustic localization and visual-inertial odometry. The experimentations show that the proposed UWAR technologies could contribute to have a better comprehension of the underwater site and its archaeological remains.

Keywords: Markerless and marker-based tracking | Underwater acoustic localization | Underwater augmented reality | Underwater cultural heritage

Abstract: The paper presents the digital technologies developed in the VISAS project and their application to the underwater archaeological site of Cala Minnola (Levanzo Island, Italy)that preserves the remains of a Roman ship. Following the basic principles defined by UNESCO for the protection of the Underwater Cultural Heritage the VISAS project has led to the development of innovative digital technologies for a more engaging and educational exploitation of the submerged archaeological sites. In particular, the paper describes a virtual diving system that allows users to perform, outside of the submerged environment, a virtual exploration of the Cala Minnola shipwreck site. Moreover, an augmented diving system provides, through an underwater tablet, a geolocalized multimedia guide for the divers that visit the underwater archaeological site. Both digital technologies allow users to perform an entertaining and interdisciplinary learning experience by receiving archaeological, historical, and biological information of the specific submerged site.

Keywords: Underwater 3D reconstruction | Underwater archaeology | Underwater Cultural Heritage | Virtual exploitation | Virtual reality

Abstract: The preservation status of an underwater cultural site can be determined as the combination of two primary factors, namely the site physical integrity, which results from the past and present interaction of the site itself with the biological/chemical agents located in the surrounding environment, and the exposure of the site to human-related threats. Methods to survey underwater archaeological sites have evolved considerably in the last years in order to face the challenges and problems in archaeological prospection, documentation, monitoring, and data collection.This paper presents a case-study of an archaeological documentation campaign addressed to study and monitor the preservation status of an underwater archaeological site by combining the quantitative measurements coming from optical and acoustic surveys with the study of biological colonization and bioerosion phenomena affecting ancient artefacts. In particular, we present the first results obtained in the survey and documentation campaign carried out during the spring - summer 2018 in the "Nymphaeum of Punta Epitaffio" located in the Marine Protected Area - Underwater Park of Baiae (Naples).

Keywords: 3D Imaging | 3D Mapping | Baiae Archaeological Park | Photogrammetry | Underwater Archaeology

Abstract: The paper presents the application of some Virtual Reality technologies developed in the Horizon 2020 i-MARECulture project to the case study of the sunken "Villa con ingresso a protiro", dated around the II century AD, and located in the Marine Protected Area - Underwater Park of Baiae (Naples).The i-MARECulture project (www.imareculture.eu), in fact, aims to improve the public awareness about the underwater cultural heritage by developing new tool and techniques that take advantage of the virtual reality technologies to allow the general public to explore the archaeological remains outside of the submerged environment.To this end, the paper details the techniques and methods adopted for the development of an immersive virtual tour that allow users to explore, through a storytelling experience, a virtual replica and a 3D hypothetical reconstruction of the complex of the "Villa con ingresso a protiro".

Keywords: 3D hypothetical reconstruction | digital storytelling | Virtual Diving | Virtual Heritage | Virtual Reality

Abstract: Aboveground biomass (AGB) is a parameter commonly used for assessing and monitoring primary productivity of grassland communities. Destructive AGB measurements, although accurate, are time-consuming and do not allow for repeated measurements as required by monitoring protocols. Structure-from-motion (SfM) photogrammetry has been proved to be a reliable tool for rapid and not destructive AGB estimations in grass systems. Three-dimensional (3D) models of fourteen 1 × 1 m2 pasture plots were reconstructed and AGB volume measured under several measurement settings. Volume-based AGB measures were regressed to AGB values resulting from destructive methods to identify the measurement settings that show the best fit. Furthermore, 3D models of four mountain pasture plots were reconstructed in May, July, and August. Models relative to the same plot were aligned and their relative difference measured to produce a diachronic canopy variation model (DCVM). On the measured volume (Vd), the coefficient of density (cρ) was applied to adjust the volume values (Vadj) in relation to variation due to different DCVM point densities. The measurement setting for AGB volume estimations strongly influenced their correlation with traditional AGB scores. The best fit was obtained selecting 1 mm grid cell size and minimum point height distance. Such options were then selected to measure the DCVM. Adjusted volumes were fully correlated with the average point distance. Three plots revealed higher rates of AGB in the spring compared to summer season, as justified by the summer aridity constraints affecting vegetation productivity in Mediterranean areas. In one plot, we found an anomalous seasonal pattern, showing an AGB reduction in spring, which can be correlated with grazing, that promoted a subsequent increment in summer. Our study indicates that image-based photogrammetric techniques allow for reliable non-destructive measurements of surface biomass in diachronic analyses, offering a valuable tool for evaluating occurrence, magnitude, and spatial patterns of variations of community primary productivity over time. Diachronic canopy variation model produced congruent patterns of inter-seasonal canopy variations proving to be a useful tool for analyzing local disturbance to vegetation canopy caused by grazing.

Keywords: biomass | coefficient of density | diachronic variation | local disturbance | non-destructive measurements | pasture community | photogrammetry | structure-from-motion

Abstract: 3D models of submerged structures and underwater archaeological finds are widely used in various and different applications, such as monitoring, analysis, dissemination, and inspection. Underwater environments are characterised by poor visibility conditions and the presence of marine flora and fauna. Consequently, the adoption of passive optical techniques for the 3D reconstruction of underwater scenarios is a highly challenging task. This article presents a performance analysis conducted on a multi-view technique that is commonly used in air in order to highlight its limits in the underwater environment and then provide guidelines for the accurate modelling of a submerged site in poor visibility conditions. A performance analysis has been performed by comparing different image enhancement algorithms, and the results have been adopted to reconstruct an area of 40 m2 at a depth of about 5 m at the underwater archaeological site of Baiae (Italy).

Keywords: 3D reconstruction | Image enhancement | Underwater Cultural Heritage | Underwater imaging

Abstract: Marine archaeologists study a large number of submerged sites of interest around the world, which require continue diving explorations and monitoring. Although technology has improved a lot the research in the underwater environment, human intervention is preferred whenever depth makes the sites accessible by divers. This paper presents the concept, the first steps and the preliminary results of the Lab4Dive project, which is co-funded by the EMFF programme of EU, that aims to design, develop, and validate an innovative, marketable and competitive product for surveying, documenting and preserving Underwater Cultural Heritage. The archaeologist will be provided with an underwater tablet equipped with environmental sensors, where a properly designed data gathering system will be accessible through a dedicated application. Lab4Dive aims also to train young researchers and to encourage multi-disciplinary cooperation through the concept of a “Blue Lab”.

Abstract: Underwater manipulation is a key technology for marine industries and exploration that can be efficiently adopted in other application fields, such as underwater archaeology, biological manipulation, scientific expedition, as well as offshore construction in the Oil and Gas industry. It is performed remotely by expert pilots thanks to the visual feedbacks provided by one or more cameras but without any information about the distance between the end-effector and the target. To this end, the paper presents a novel system based on a sensorized robotic arm, stereoscopic 3D perception and augmented reality visualization to support ROV's pilots in underwater manipulation tasks. The system, thanks to the adoption of an optical-stereo camera, provides a visual feedback of the underwater scene on which a depth map of the underwater workspace is augmented on. In particular, combining the kinematics of the robotic arm and the standard photogrammetric model of the stereo camera, it is possible to generate a depth map that shows to the pilots the distances of the surface of the scene objects from the end-effector's pose. Experimental tests carried out in the context of the CoMAS (In-situ conservation planning of Underwater Archaeological Artefacts) project have demonstrated the effectiveness of the proposed system.

Keywords: Augmented reality | Forward kinematics | Optical-stereo camera | Underwater manipulation

Abstract: The Underwater Cultural Heritage represents a key aspect of our historical memory still little known due to a number of limitations imposed by the underwater environment. The aim of this paper is to explore the use of digital three-dimensional reconstructions to support the research about this immeasurable archaeological and historical resource. The whole virtual reconstruction process is described step by step, focusing on the iterative feedback allowing for reaching the best virtual reconstruction solutions, helping the archaeologists to better focus their reasoning through a detailed visual representation, and the technical experts to avoid misleading details in the final virtual reconstruction.

Abstract: The paper presents a virtual diving system based on a virtual reality (VR) application for the exploitation of the Underwater Cultural Heritage. The virtual diving experience has been designed to entertain users, but its added pedagogical value is explicitly emphasized too. In fact, the ludic activities, consisting in the simulation of a real diving session from the point of view of a scuba diver, are following a storyline described by a virtual diving companion who guides users during the exploration of the underwater archaeological site. The virtual diving system provides general and historical-cultural contents, but also information about the flora and fauna of the specific submerged site to the users. The results collected through user studies demonstrate that the proposed VR system is able to provide a playful learning experience, with a high emotional impact, and it has been well appreciated by a large variety of audiences, even by younger and inexperienced users.

Keywords: Serious games | Underwater archaeological sites | Underwater Cultural Heritage | Virtual diving system | Virtual reality

Abstract: UCRCA - Underwater Cultural Routes in Classical Antiquity" is an eu project financed through the easme-emff fund in order to promote the creation of touristic thematic itineraries linked to the underwater archaeological heritage. It aims to enhance the sustainability of the touristic sector in coastal and maritime areas through the broadening of the cultural tourism offer, thanks to the creation of underwater itineraries for recreational diving activities. Four pilot sites bearing specific characteristics have been chosen to create and launch a new touristic product, two in Greece and two in Southern Italy. Alonissos Island (Sporades), Methoni (Peloponnese), San Pietro in Bevagna (Puglia) and Crotone (Calabria) are four popular holiday destinations in the Mediterranean Sea, whose archaeological underwater sites are still unnoticed by the greater audience. Before creating archaeological underwater itineraries, the Italian Institute for the Conservation and Restoration (MiBAC-iscr) and the Department of Mechanical and Management Engineering of the Calabria University (dimeg-unical) carried out several years of activities linked to the research and test of new methods and technologies for the in situ conservation of the underwater artifacts.

Keywords: European community | In situ preservation | Responsible tourism | Shipwrecks | Underwater archaeological heritage | Underwater archaeology | Underwater restoration | Underwater tourism

Abstract: The Underwater Cultural Heritage (UCH) represents a vast historical and scientific resource that, often, is not accessible to the general public due the environment and depth where it is located. Digital technologies (Virtual Museums, Virtual Guides and Virtual Reconstruction of Cultural Heritage) provide a unique opportunity for digital accessibility to both scholars and general public, interested in having a better grasp of underwater sites and maritime archaeology. This paper presents the architecture and the first results of the Horizon 2020 i-MARECULTURE (Advanced VR, iMmersive Serious Games and Augmented REality as Tools to Raise Awareness and Access to European Underwater CULTURal heritage) project that aims to develop and integrate digital technologies for supporting the wide public in acquiring knowledge about UCH. A Virtual Reality (VR) system will be developed to allow users to visit the underwater sites through the use of Head Mounted Displays (HMDs) or digital holographic screens. Two serious games will be implemented for supporting the understanding of the ancient Mediterranean seafaring and the underwater archaeological excavations. An Augmented Reality (AR) system based on an underwater tablet will be developed to serve as virtual guide for divers that visit the underwater archaeological sites.

Keywords: Serious games | Underwater Archaeological sites | Underwater Augmented Reality system | Virtual museums

Abstract: The paper presents the application of the technologies and methods defined in the VISAS project for the case study of the underwater archaeological site of Cala Minnola located in the island of Levanzo, in the archipelago of the Aegadian Islands (Sicily, Italy). The VISAS project (http://visas-project.eu) aims to improve the responsible and sustainable exploitation of the Underwater Cultural Heritage by means the development of new methods and technologies including an innovative virtual tour of the submerged archaeological sites. In particular, the paper describes the 3D reconstruction of the underwater archaeological site of Cala Minnola and focus on the development of the virtual scene for its visualization and exploitation. The virtual dive of the underwater archaeological site allows users to live a recreational and educational experience by receiving historical, archaeological and biological information about the submerged exhibits, the flora and fauna of the place.

Keywords: Underwater 3D reconstruction | Underwater cultural heritage | Virtual exploitation | Virtual reality

Abstract: The paper presents an outcome of the VISAS project (www.visas-project.eu) that concerns a virtual reality application for the exploitation of the underwater cultural heritage. The VR system takes advantage of novel 3D reconstruction techniques to provide geolocated and multi-resolution textured 3D models of underwater archaeological sites. Within the virtual underwater sites users live a recreational and educational experience by receiving historical, archaeological and biological information and contents about the submerged exhibits and structure of the site. Furthermore, the VR system allows divers to make a detailed planning of the operations and itinerary that will be later performed in the underwater environment.

Keywords: underwater 3D reconstruction | Underwater cultural heritage | VR systems

Abstract: On November 2, 2001, the UNESCO Convention on the Protection of the Underwater Cultural Heritage provided a detailed state cooperation system and set out the basic principles for the protection of underwater cultural heritage. To date, the Convention has been ratified by 51 countries. One of the four main principles states that the in situ preservation of underwater cultural heritage should be considered as the first option before allowing or engaging in any further activities. In accordance with these principles and recommendations, in the last years many projects intended for developing and testing new techniques and tools to support in situ conservation of underwater archaeological remains have been funded and are now underway. This paper describes the contribution of the CoMAS project (In situ conservation planning of Underwater Archaeological Artifacts—http://www.comasproject.eu), funded by the Italian Ministry of Education, Universities and Research (MIUR) and run by a partnership of private companies and public research centers. The CoMAS project aims at the development of new materials, techniques, and tools for the documentation, conservation, and restoration of underwater archaeological sites in their natural environment. The paper describes in detail the results achieved during the project in the development of innovative materials, mechatronic tools, and armed remotely operated vehicle systems that can efficiently support the restorers' work in all their activities for preserving underwater cultural heritage in its original location on the seafloor.

Keywords: 3D imaging | Mechatronics | ROV | Underwater archaeological restoration | Underwater archaeology

Abstract: The integration of underwater 3D data captured by acoustic and optical systems is a promising technique in various applications such as mapping or vehicle navigation. It allows for compensating the drawbacks of the low resolution of acoustic sensors and the limitations of optical sensors in bad visibility conditions. Aligning these data is a challenging problem, as it is hard to make a point-to-point correspondence. This paper presents a multi-sensor registration for the automatic integration of 3D data acquired from a stereovision system and a 3D acoustic camera in close-range acquisition. An appropriate rig has been used in the laboratory tests to determine the relative position between the two sensor frames. The experimental results show that our alignment approach, based on the acquisition of a rig in several poses, can be adopted to estimate the rigid transformation between the two heterogeneous sensors. A first estimation of the unknown geometric transformation is obtained by a registration of the two 3D point clouds, but it ends up to be strongly affected by noise and data dispersion. A robust and optimal estimation is obtained by a statistical processing of the transformations computed for each pose. The effectiveness of the method has been demonstrated in this first experimentation of the proposed 3D opto-acoustic camera.

Keywords: Optical and acoustic integration | Opto-acoustic vision | ROV navigation | Underwater 3D imaging

Abstract: This paper presents an experimentation, which has been conducted in the underwater archaeological site of Capo Colonna, aimed to verify the joined use of optical and acoustic techniques for the generation of multi-resolution textured 3D models of underwater sites, obtained by merging the results of surveys carried out with these two types of systems.

Abstract: The underwater cultural heritage is an immeasurable archaeological and historical resource with huge, but yet largely unexploited, potentials for the maritime and coastal tourism. In this regard, in the last years, national and international government authorities are supporting and strengthening research activities and development strategies, plans and policies to realize a more sustainable, responsible and accessible exploitation of the underwater cultural heritage. To this end, the paper presents the architecture of a new system that, taking advantage of the modern virtual and augmented reality technologies, allows diver and non-diver tourists to make a more engaging and educational experience of the underwater archaeological sites. This system has been developed and tested in the VISAS project (www.visasproject. eu) that aims to the enhancement of the cultural and tourist offer related to the underwater archaeology through innovation of modes of experience, both on site and remote, of the underwater environments of archaeological interest.

Keywords: AR systems | Underwater 3D reconstruction | Underwater cultural heritage | VR systems

Abstract: Remotely Operated underwater Vehicles (ROVs) play an important role in a number of operations conducted in shallow and deep water (e.g.: exploration, survey, intervention, etc.), in several application fields like marine science, offshore construction, and underwater archeology. In this work we describe the preliminary steps in the development of the set-up of a special ROV addressed to perform the monitoring and the planned maintenance activities required to prevent the biological colonization in an underwater archeological site. In order to perform these operations, the ROV has been equipped with a custom arm and an opto-acoustic camera. To simultaneously satisfy position and force trajectory constraints, the vehicle-manipulator system is also controlled through a hybrid positionforce control scheme.

Keywords: opto-acoustic 3D camera | ROV control | sensorized arm

Abstract: Remotely Operated underwater Vehicles (ROVs) play an important role in a number of operations conducted in shallow and deep water (e.g.: exploration, survey, intervention, etc.), in several application fields like marine science, offshore construction, and underwater archeology. ROVs are usually equipped with different imaging devices, both optical and acoustic. Optical sensors are able to generate better images in close range and clear water conditions, while acoustic systems are usually employed in long range acquisitions and do not suffer from the presence of turbidity, a well-known cause of coarser resolution and harder data extraction. In this work we describe the preliminary steps in the development of an opto-acoustic camera able to provide an on-line 3D reconstruction of the acquired scene. Taking full advantage of the benefits arising from the opto-acoustic data fusion techniques, the system was conceived as a support tool for ROV operators during the navigation in turbid waters, or in operations conducted by means of mechanical manipulators. The paper presents an overview of the device, an ad-hoc methodology for the extrinsic calibration of the system and a custom software developed to control the opto-acoustic camera and supply the operator with visual information.

Keywords: 3D opto-acoustic camera | Optical and acoustic data fusion | ROV guidance | Stereovision system | System calibration

Abstract: This paper presents some experimentations, which have been conducted in the submerged archeological Park of Baiae, aimed to identify the problems related to the underwater 3D documentation process. The first test has been addressed to verify if a dense stereo mapping technique, usually employed in terrestrial and aerial applications, might be employed in critical underwater conditions by assessing the influence of different factors on the results. In the second test, the accuracy of the 3D model obtained through this technique has been evaluated. The third test deals with the geo-localization of the 3D models, conducted by merging the optical and acoustic data, through a multi-resolution bathymetric map of the site as a reference.

Keywords: 3D documentation | 3D model accuracy | 3D reconstruction | Baiae archeological park | Optical and acoustic data merging

Abstract: Seagrass communities are considered one of the most productive and complex marine ecosystems. Seagrasses belong to a small group of 66 species that can form extensive meadows in all coastal areas of our planet. Posidonia oceanica beds are the most characteristic ecosystem of the Mediterranean Sea, and should be constantly monitored, preserved and maintained, as specified by EU Habitats Directive for priority habitats. Underwater 3D imaging by means of still or video cameras can allow a detailed analysis of the temporal evolution of these meadows, but also of the seafloor morphology and integrity. Video-photographic devices and open source software for acquiring and managing 3D optical data rapidly became more and more effective and economically viable, making underwater 3D mapping an easier task to carry out. 3D reconstruction of the underwater scene can be obtained with photogrammetric techniques that require just one or more digital cameras, also in stereo configuration. In this work we present the preliminary results of a pilot 3D mapping project applied to the P. oceanica meadow in the Marine Protected Area of Capo Rizzuto (KR, Calabria Region-Italy).

Keywords: 3D mapping | 3D reconstruction | Optical instruments | Posidonia oceanica | Quality status