ABSTRACT:Μodern advances in the field of image-based 3D reconstruction of complex architectures are valuable tools that may offer the researchers great possibilities integrating the use of such procedures in their studies. In the same way that photogrammetry was a well-known useful tool among the cultural heritage community for years, the state of the art reconstruction techniques generate complete and easy to use 3D data, thus enabling engineers, architects and other cultural heritage experts to approach their case studies in an exhaustive and efficient way. The generated data can be a valuable and accurate basis upon which further plans and studies will be drafted. These and other aspects of the use of image-based 3D data for architectural studies are to be presented and analysed in this paper, based on the experience gained from a specific case study, the Plaka Bridge. This historic structure is of particular interest, as it was recently lost due to extreme weather conditions and serves as a strong proof that preventive actions are of utmost importance in order to preserve our common past.

The aim of this paper is to present the specific methods by which 3D scanning and photogrammetric techniques were incorporated into the architectural study, the documentation and the graphic restoration study of the monument of the ancient theatre of Nikopolis. Traditional methods of surveying were enhanced by the use of 3D scanning and image-based 3D reconstruction and 3D remodelling and renderings. For this reason, a team of specialists from different scientific fields has been organized. This presented the opportunity to observe every change of the restoration design process, not only by the use of common elevations and ground plans, but also in 3D space. It has been also very liberating to know how the monument will look like in this unique site after the restoration, so as to obtain at the study stage the best intervention decisions possible. Moreover, these modern work tools helped of course to convince the authorities for the accuracy of the restoration actions and finally to make the proposal clear to the public.