From project drawings to digital modeling in different representation scales. The Citadel of Alessandria

The spatial reality and the easy view of 3D virtual representations constitute a useful basis to accommodate themes like periodization of the buildings related to specific events, and phenomenology (e.g. transformation, restoration, ecc.). The following approach is mandatory for the understanding of any of th e transformation phases occurred to the historical architectural manufact. The first step is the definition of the geometric-dimensional limits of the area under investigation, the definition of the level of accuracy to be achieved in the three-dimensional survey and the definition of the representation’s deliverables that must be produced, according to the objectives of the documentation process. The second step is the search and recover of historical sources: maps, floor plans, sections and elevations, axonometric views, images, sketches. The aim of this work is to demonstrate that for Cultural Heritage assets, already surveyed and/or documented in some way in the past, 3D modeling could be possible at the level of detail allowed by the contents of the his torical sources themselves. The test will be carried out on the Citadel of Alessandria (Italy) and used for recovery plans, planned reuse and enhancement. The work constitutes the first step of a more wide project related to the formalization of a "digital network of fortifications" in Europe.