Georeferencing of historical iconography for the knowledge of the built heritage

The purpose of this paper is to show, starting from practical examples, how georeferencing in GIS environment can favour a detailed knowledge of the architectural heritage. This tool works on a large range of images and allows to detect changes not only in the volume of the building but also how it has developed in the surroundings and moreover it can get useful information to understand how particular deteriorations have occurred. The suggested approach wants to be a non-destructive method to analyse the historical building, particularly cheap if a free open-source version is chosen. Furthermore, this technique is understandable even by non-experienced people who can read these results easily, since they are learned through visual language.