THE REVERSE MODELLING REALIZED BY DIGITAL SCANS AND FOTOMODELLAZIONE: BASED ON POST-PROCESSING COMPARED SEVERAL NOTEWORTHY EPISODES CONTAINED IN THE BASILICAL COMPLEX OF SAN LORENZO FUORI LE MURA IN ROME

Abstract. In the last decade, the subject area of the survey, and also that of representation, have undergone major changes with the introduction and use of advanced technologies that have revolutionized both the operational processes dedicated to the withdrawal of the measures that those graphic display data in terms of return and performance. The three-dimensional vision deriving from direct observation, or photogrammetric instrumental with the application of images, constitutes the most complete display means of the formal, morphological and material aspects of the detected object. 3D modeling offers many advantages, such as managing even the most complex geometric surfaces and its use is investing many sectors: in particular in the field of architecture serves many purposes including documentation, representation, diagnostics, materials and degradation, the enhancement and conservation of the property, etc.. The laser scanner technology together with that of fotomodellazione, is aimed to the acquisition, modeling and rendering threedimensional (3D) surface observed physical. The laser system to scan, as well as that of photographing, provides as a direct result of the measurement session a set of three-dimensional coordinates, in a reference system linked with the instrument. The high amount of sampled data, in the order of thousands per second, allows to obtain a high level of detail offering an acquisition that could be called pseudo-continuous. In this context, there is a complex major project work on the Basilica di San Lorenzo flm in Roma, – whose first partial results have recently been published – in the course of an activity which has been carried out to study and research for the establishment of procedures for processing the most appropriate and valid to be applied during post-processing for the eventual realization of a proper three-dimensional model. This paper will illustrate, through the analysis of some significant episodes of the Basilica, as the criteria adopted for the choices made at this stage have been crucial to the final outcome.