UWAR: a tailored application for Underwater Augmented Reality to access Underwater Cultural Heritage
The challenge
The Mediterranean Sea has a huge cultural and archaeological asset, consisting of ancient shipwrecks and sunken cities, with broad potential for the development of the tourism sector. Furthermore, the latest advances in the field of survey techniques for the exploration of the seabed is exponentially increasing the discovery of underwater cultural heritage (UCH) sites. Nevertheless, many of them are not accessible because of the limitations due to the environmental context, such as depth of the site and sea currents, or to local and international laws and regulations. Furthermore, those that can be visited by diver tourists present some issues related to the marine environmental conditions that do not permit a satisfactory exploitation of the underwater archaeological sites. Simultaneously, the UCH has provoked considerable interest thanks to the work carried out in recent years by the National Commissions for UNESCO that discourages the adoption of the traditional excavation and recovery methods in favour of on-site examination and in situ preservation and conservation techniques.
Due to water turbidity and biological colonization, in the submerged archaeological sites the divers often suffer from low visibility conditions and this leads to a less understanding of the underwater environment and a higher probability for them to miss the sense of direction. Unfortunately, GNSS sensors (GPS, GLONASS, and Galileo) are inadequate to this end since their signals are absorbed in water after a few centimetres below sea level. Furthermore, guided or accompanied archaeological diving tours are carried out with experienced divers, but it is not possible to perform a fluid and direct communication unless they use full-face diving masks or analogous dedicated equipment. At the moment, there are few attempts to support the divers by facilitating their comprehension of the archaeological context during a diving session.
On the other side, computer graphics techniques like 3D reconstructions, Virtual Reality (VR) and Augmented Reality (AR), have demonstrated to be a highly effective means of communication for facilitating the access and increasing the value and the public awareness about the cultural heritage. In particular, AR technologies could be a useful tool to overcome these limitations and could be a valid solution to improve the readability and understandability of the submerged archaeological sites and enhance the overall diving experience by providing interesting information about the ancient remains and artefacts.
A system composed of a waterproof tablet and an underwater localisation system, named Divy, has been designed and developed to support divers’ navigation and exploration. It enables the divers to access different features such as the visualization of a map of the underwater site that allows them to know their position within the submerged site, the possibility to acquire geo-localized data, the visualization of additional information about specific points of interest and the communication with the surface operators through an underwater messaging system.

The goal: Underwater Augmented Reality
The UnderWater Augmented Reality (UWAR) concept applied in Underwater Cultural Heritage (UCH) sites has been designed and developed in the context of the Horizon 2020 iMARECulture (Advanced VR, iMmersive Serious Games and Augmented REality as Tools to Raise Awareness and Access to European Underwater CULTURal hEritage) project, which aimed to investigate and develop AR-based solutions for promoting and improving the public awareness about the UCH.
The UWAR feature is provided to the user through Divy. The Augmented Reality (AR) within a scuba dive is intended to provide the diver with a new and more immersive experience compared to a classic recreational dive. The AR allows the diver to view the hypothetical reconstruction of the structures and artefacts that are superimposed on the present status of the underwater archaeological site. The user can activate the UWAR feature in correspondence with specific AR Zones, that are displayed in an overlay over a map of the underwater site. He/she can switch between the visualization representing the actual conditions of the ancient ruins in the underwater site and the hypothetical 3D reconstruction of how the site appeared in the past. Moreover, the diver can choose the type of visualization between the top-view and the first-person view. The top-view is especially suitable to orientate in the underwater environment whereas the first-person allows to fully enjoy the AR view modality. While in AR modality and first-person view, the user can move around the tablet, rolling and pitching, in order to change the point-of-view of the camera.

Where we are? Underwater geo-localisation It is well known that the ordinary Global Positioning System (GPS) fails to provide location underwater. The reason is that the electromagnetic signals from the orbiting satellites are heavily damped in water. As regards Divy, the geo-localisation is provided by an acoustic localization system, but this kind of technology suffers from a low update rate, and cannot be employed alone for the UWAR purpose. An innovative technique has been conceived, that support the localisation system with pictures coming from a camera that are analysed through Visual Inertial Odometry (VIO) techniques, to improve the quality of the localisation information and provide the users with a smooth AR visualization.

Underwater Archaelogical Park of Baia: Villa con ingrsso a Protiro
The first submerged site where the UWAR technology has been deployed is the Marine Protected Area - Underwater Archaeological Park of Baiae, located in the volcanic area of the Phlegrean Fields, a few kilometres North of Naples (Italy). This is a worldwide known site because it is a typical representative of the phenomenon of bradyseism as the rests of the Roman age are actually at a depth ranging from 0.0 m to 15.00 m from the sea level, and only a few ruins are still on the coastline, inland. The Underwater Park of Baiae is famous also for its extensive submerged area of 176.600 hectares, and the wide range of different architectural structures, i.e., fisheries and harbour buildings, thermal baths, residential buildings, and villas, with some decorations that are still preserved. In particular, the ruins of the “Villa con ingresso a protiro - Villa with Vestibule”, dated to the first half of the II century AD, have been brought back to life thanks to the UWAR.

The UWAR App has been developed within the framework of the iMARECulture project, which has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 727153.
Content provider: Ministero della Cultura, Istituto Centrale per il restauro
Permission to publish data (3D site, 3D finds, photos and video): Ministero della Cultura, Istituto Centrale per il restauro, Parco Archeologico dei Campi Flegrei

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