3D data integration for the digital reconstruction of cultural heritage monuments

The ancient city centers often contain traces of monuments almost completely disappeared, whose few remains are hidden by modern buildings. This is the case for many monumental buildings of the Roman period in Italian cities, that have almost disappeared over time being gradually dismantled for the reusing their construction materials, leaving space to a dense urbanization. Knowledge of such monuments is often approximate and based on historical memories of various kinds. In such situations, three-dimensional surveys and digital 3D modelling reconstructions can be of great support for scientific-archaeological research and for providing a scientifically supported image of cultural heritage sites.This paper shows the work on the emblematic example of the late Roman Circus of Milan, an impressive monument of about 450x85 meters, built when Mediolanum used to be capital of the Western Roman Empire (286-402 A. D). This fact is nowadays almost unknown to most citizens of Milan. The diachronic reconstruction approach is used in order to show the monument in his current state and in his presumed past aspect. The reconstruction is based on a proper mix of quantitative data originated by 3D surveys at present time, and historical sources like ancient maps, drawings, archaeological reports, archaeological restrictions decrees and old photographs. In this panorama, the georeferenced acquired data of the remains play a key role in order to validate the previous reconstruction of the building and to define some fixed points to hypothesize a reliable reconstruction of the area in different historical periods. The experimental activity is defined by the project Cultural Heritage Through Time - CHT2 (http://cht2-project. eu), funded in the framework of the Joint Programming Initiative on Cultural Heritage (JPI-CH) of the European Commission.