Digital Survey for Cultural Heritage Safeguard: Saint John Tower in Enna

Cultural heritage is an important richness for future generations both as historical memory of the past, which tells the roots of our culture, and from a strictly economic point of view. As a matter of fact, cultural heritage -natural and builtis a source of attraction of investment on the territory that, investing on economy of culture, produces a virtuous circle able to generate an economicmonetary benefit on the territory itself. That being stated, it is an ethical obligation for all of us scholars, guardian of the past, to hand down to future generations this heritage undamaged and, above all, preserving its identity. It is necessary, before any preservation and conservation work, to trace backwards the history of the cultural asset by means of survey. As a matter of facts survey is a knowledge tool which allows to investigate thoroughly both the project idea and the material execution, the shape and the dimension, the being and the essence of the work. Nowadays, thanks to survey innovative technologies, such as laser scanning, it is possible to obtain acquisition data models that record and document cultural assets' dimensional, material and decay features. 3D Models that, in addition to constitute a data base of information, are a documentary heritage on which it is possible carry out different investigations. This study deals with the research conducted on the medieval Saint John tower in Enna, which was the tower of façade of the homonymous church built in the 13th c. In the survey phase we used digital advanced instruments so that the accuracy of the measure should allow exhaustive hypothesis on architectural handiwork: a critical survey of the current situation and of the changes due to restoration works. As a matter of facts, the materic and dimensional information extracted from the numeric model – point cloud – have been essential to understand the features which connote the handiwork. The accuracy of scans detail made readable masonry texture, materials decay and instability, being a valid aid for carrying out punctual thorough investigations. Moreover, it has been possible to conduct a critic survey, verifying in retrospect both the geometry of the vaulted porch of the ground floor and the geometrical compatibility of the proposed and realized solution for roofing vault due to restoration works made by arch. Valenti in 1921. Indeed the comparison among the surveyed data, the iconographic sources (Walter Leopold surveys) and the geometric studies carried out revealed the inappropriate work of reconstruction of the roofing vault. The results of this study testify once again the relevant and essential role performed by survey as instrument of knowledge investigation aimed to an accurate and exhaustive documentation of cultural heritage and to a conscious restoration work respectful of the essence of architecture.