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Regeneration of cartographic heritage in a digital form offers a new opportunity of preserving and studying historical cartography. Modern digital techniques coming from Geomatics science help in metric analysis of ancient maps and, when integrated with the contribution from other disciplines, can allow specific studies otherwise unachievable. The study subject is the first establishment urban map of the nineteenth century Gregorian Cadastre of Bologna, today kept at the local State Archives. The uniqueness of this cadastral cartography is to be composed by ground-floor maps and separate maps for the single floors above and below; written documentation on land lots completes the cadastre. In the study, digital tools deriving from the integration of geomatic techniques (in particular georeferencing, GIS, 3D modelling) and archive skills are used to deeply analyze this peculiar cadastre, once converted in a digital form and metrically processed. For some test areas, a comparative consultation of the graphical information stored in the georeferenced maps, and the written one in the related cadastral registers is performed; this allows rigorous 3D digital reconstructions of the cadastral properties, and a new thematic visualization. This modern kind of representation turns to be a powerful and expressive tool to deeply analyze the complex nineteenth century arrangement of the city, highlighting some interesting aspects which otherwise would remain invisible. Furthermore, the tool allows users to get information about the Gregorian Cadastre in a simpler way than searching the original documents; this way, moreover, avoiding any damage of the delicate ancient maps.

The research focuses on the first establishment urban map of the nineteenth century Gregorian Cadastre of Bologna, kept today at the State Archives of the city. In this cadastral cartography the city is divided into some sectors; for each sector – unique case in the Gregorian Cadastre of the ancient Papal State – there are ground floor maps and maps for the floors above and below. The present study aims to analyse this peculiar cadastre using digital tools deriving from the integration of geomatic and archival skills. For some test-areas, a careful comparative consultation of the graphical information stored in the georeferenced maps and the writ-ten one in the related cadastral registers is performed; this allows 3D digital reconstruc-tions of the horizontal and vertical extent of the cadastral proprieties, and also thematic visualizations (e.g. according to owners, designed use, rent, etc.). This modern kind of representation allows a deep analysis of the complex nineteenth century arrangement of Bologna – still preserved in the ancient Gregorian Cadastre of the city –, highlighting some interesting aspects which otherwise would remain invisible. Thus, it turns to be a powerful tool of analysis for historians and city planners.

The presented research focusses on the first establishment urban map of the nineteenth century Gregorian Cadastre of Bologna, kept today at the National Archive of the city. In this cadastral cartography the city is divided into some sectors; for each sector – unique case in the Gregorian Cadastre – there are ground floor maps and maps for the floors above (5 floors) and below (2 floors). The present study aims to acquire a deep understanding of this rare multi-storey arrange-ment of the cadastral maps, focusing on a little but special group of cadastral lots in the centre of the city. By means of the graphical information stored in the georeferenced maps, coupled with the written one in the cadastral registers, a reconstruction of the hori-zontal and vertical extent of the cadastral proprieties which overlap each other on the little group of lots was possible, and the result was displayed by means of a three-dimensional digital model. By comparing the latter to the appearance of the city given by both previous scenographic maps and the reality of today, it is possible to state that the multi-storey structure of the Gregorian Cadastre of Bologna was not intended to describe the vertical extent of the buildings, but to experiment with a tool for raising taxes on urban buildings in a more precise way, by means of criteria which seem to anticipate the subsequent land register recording by real estate units. Unfortunately, the sophistication of such a system probably advised against its extension to other realities of the Papal State, making the Bo-logna experiment an isolate – even if for this reason more interesting – attempt.

The plan, being project tool and representation at the same time, allows an understanding, by means of ancient cartography, of the ancient city as an entity with its own identity connotation, whose definition derives mainly from the clarity of the construction rule which permitted its realization. The present study analyzes the main theoretical and technical questions which concern the urban architecture of Bologna between the 18th and 19th centuries, by means of historical maps and in particular the Gregorian Cadastre., Il piano come strumento di progetto e al tempo stesso come rappresentazione consente di comprendere attraverso le carte storiche la città del passato come entità dotata di una sua connotazione identitaria che deve gran parte della sua definizione alla chiarezza della regola costruttiva che ne ha sostanziato la realizzazione. Il contributo individua le principali questioni teoriche e tecniche legate all’architettura urbana a Bologna tra Settecento e Restaurazione, studiata attraverso la cartografia storica in generale e il Catasto Gregoriano in particolare., DISEGNARECON; Vol. 5, Numero Speciale (2012) - DOCO 2012, a cura di R. Mingucci, C. Bartolomei, L. Bravo, S. Garagnani; 255-264

The study focuses on the nineteenth century Gregorian Cadastre of Bologna, kept today at the State Archive of the city. In these maps the city is divided into several sectors; for each sector there are ground floor maps and maps for the floors above and below. In the study, results from metric analysis of these maps are reported. The analysis consists in a preliminary georeferencing of digital images derived from high quality scanning of the original documents, together with an assessment of map deformation. Moreover, digital mosaics from each floor were sequentially superimposed. Finally, a comparison with the original edition map kept at the State Archive of Rome was performed, in order to highlight possible differences between the two editions and digitally restore the worn maps of the Bologna edition.