Italy is one of the countries with the highest concentration of art in the world. Protection of this heritage requires the contribution of science and technology, and targeted funding. In response to a specific call for bids, in 2001 the consortium SIINDA (Sistemi Innovativi di Indagine e Diagnosi Assistita - innovative systems for computer-aided investigation and diagnosis) was set up to develop a research project bearing the same name. Consortium members are three private companies and four public bodies (including CNR). Its goal is to develop an integrated system for cultural heritage, in particular for the Roman Theatre in Aosta (the Aosta Autonomous Regional Government is a Consortium member).
As a consequence, an "active stereovision system" (SVA) has been developed. It consists of three digital cameras -a wide-angle and two telephotos-. The latter two are mounted on rotary tables, in turn mounted on a rotating body with orthogonal axis. Guided by the wide-angle camera, the two telephoto cameras rotate until aiming at the same target. The measurement of the three angles results by triangulation in the spatial coordinates of the target, and enables to re-establish the reference system, for example after restoration or periodic inspections. The images enable additional integrated measurements, namely colorimetric (for each pixel), automatic detection of mark points (natural targets for camera convergence, and for "navigating" the image), and reconstruction of surface texture. The SVA is a cooperation of the IMGC-CNR, the IEIIT-CNR and the IEN. The IMGC is responsible for the mechanical design, manufacture and adjustment of the instrument, and of coordinate measurements. The IEIIT is responsible for image processing, reconstruction of surface texture, graphical user interface, and system integration. The IEN is concerned with the stereovision and with colorimetric measurements.
The SVA has 18 µrad angular resolution, resulting in 50 µm resolutions in the image plane, and 400 µm in the line of sight, for an object at 3 m distance. In the 2003 alternative adjustment techniques were investigated and compared. This required to design and manufacture a 800 mm linear dimensional artefact bearing 6 target easily detected by cameras, fully made in invar (special steel with low thermal expansion) to allow use in open air. On-field tests held on the Roman Theatre in Aosta, aimed at comparing the coordinates of targets attached to the monument as measured by the SVA and by traditional photogrammetry, achieved an agreement within 2-3 mm.
This collaboration between public and private research bodies is at the service of Italy's artistic and cultural heritage.
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