Cartographic models for a diachronic analysis of the urban image of Rome

Considering the physical elements of the city system as the material expression of all the evolutionary phenomena of sites, its representation can be considered as a system of general knowledge capable of coalescing heterogeneous information. The enormous changes that take place in cities over the years have determined an evolution of the morphological variations in the territorial setup, in the architectural stratification of the urban structure and in the perception and use of urban space. If urban space is considered as a place where people interact, then bibliographical, iconographic and cartographic sources contribute to providing a diachronic reconstruction of the urban fabric, which is possible thanks to the historical representations produced over the years, which are sometimes symbolic if not metaphorical: these representations make it possible to understand the sites even if their accuracy is debatable. The use of computer science in survey and cartographic representation and the creation of regional IT systems has made it possible not only to establish interlinked georeferential databases, but above all facilitate multiple consultation and later elaboration. Digital cartography used to create three-dimensional models is therefore a way to review space - not on the basis of planimetric explorations but by creating virtual models more or less automatically generated based on the cartography itself. Three-dimensional cartography should be studied to identify specificities and details present in the restitution of the urban space; these characteristics immediately prompt one to try and use the same representative exuberance to reconstruct the historical past of the city or at least of some of its more important periods, especially the changes in its orography and constructions. The city of Rome is a paradigmatic example of a historical stratification that has constantly reused the same sites and physical structures and is unique insofar as its destiny as a modern capital dates back to the eighth century B.C. But real continuity belongs to the present because the kinetic and three-dimensional image seen by anyone walking the streets of Rome projects a range of different portraits of its historical past. The centre of Rome is an excellent study area also because it has a technically good selection of sufficiently continuous cartographic records to allow comparison between the different iconographic sources, on the one hand starting from the classical period with the Forma Urbis and the maquette by Gismondi which represent – albeit with their undeniable approximations - a good starting point, and, on the other, the 3D digital cartography made in 2000.