Reconstruction of archaeological features in the Mediterranean coastal environment by means of non-invasive techniques and digital museums (Selected paper in BAR –S2079, 2010 Making History Interactive. Computer Applications and Quantitative Methods in Archaeology (CAA))

Archaeological prospection and excavation of an ancient settlement is a slow, careful and consequently costly operation. In the Mediterranean region, cities were often built next to the coastline, in order to provide bases for trade along the most convenient pathway of the time - the sea. Prospection of such sites is particularly difficult and slow because these cities are buried or sunk into the sea. The need arises for a comprehensive prospection, that can delineate the areas of further direct investigations. Results can also have a cultural and touristic value before the full site excavation by means of high resolution renderings and 3D digital representations of the subsurface. This work deals with the development and the application of an integrated methodology and visualization techniques for 3D rendering of geophysical data of the buried and submerged archaeological features in complex environment such as coastal planes. In this work we present the results from marine and ground geophysical prospections of the Phoenician, Punic and Roman town of Nora, in the South Coast of Sardinia and the Roman town of Pollentia, in the North East of the Mallorca Island. The lagoon, close to Nora, was investigated with a continuous marine electrical resistivity tomography and with the sub bottom profiler survey to find features linked to the presence of the ancient harbour. Measures were carried out by means of a customised catamaran, appositely developed for the marine geophysical surveys in shallow water. The data processing led with: 1) the reconstruction of resistivity sections and 3D renderings; 2) the comparison between the electrical and the sub bottom profiler survey results. This latter step permitted to identify some structures related with the main features observed by the sub bottom profiler; in particular we found a channel that could be the access to the ancient harbor. Near the lagoon in the surroundings of the ancient town a georadar survey was carried out in order to find the old amphitheatre. The 3D reconstruction of old roads, aqueduct and of a small part of amphitheatre was made in a critical environment. Diggings confirmed exactly the reconstruction. In the Pollentia site, we stress the rule of the geophysical investigation in un-explored to map the near surface archaeological features and exploit high resolution information acquired by electrical and georadar investigation for a realistic 3D rendering of the main features, for a virtual museum of the buried settlements. The geophysical data pointed out the presence of several well organised features that are related to the buried rests of the ancient walls of the town. Starting from the 3D rendering of the main geophysical anomalies, we applied techniques for virtual imaging of the ancient town. We tested both commercial and open source technologies based. Former has a limited access to the model because it needs a dongle key and consequently doesn’t allow a wide scale diffusion of results, so we developed a software tool based on the open source VRML technology