The Metric Documentation of Villa Poiana by Andrea Palladio with Spherical Photogrammetry

Multi-image panoramas are normally used extensively for virtual tours and documentation of Cultural Heritage for their easiness and completeness. Moreover they have metric capabilities enabling the 3d evaluation of an object provided at least two panoramas (Fangi, 2007, 2008). The procedure already very well tested, is highly efficient and fast, has been applied for the metric documentation of Villa Poiana (Poiana Maggiore, Vicenza, Italy). Villa Poiana was designed by Andrea Palladio (1508-1580) between 1540 and 1560. The Villa, in which the author reaches an absolutely synthetic and essential language, almost metaphysical, is presented as one of the more interesting works of the architect. Owned today by the CISAP (International Centre for Studies "Andrea Palladio" of Vicenza) the Villa is open to the public. The great noble floor known for its great architectural forms can be visited. One is struck by the richness and elegance of its internal equipment decorated by the painters Bernardino India and Anselmo Canera and the sculptor Bartolomeo Ridolfi. The survey and the modelling of the Villa falls within a broader study in collaboration with the CISAP about historical surveys of Palladian work for the preparation of a critical catalogue. This study shows the lack of documents relating to the Villa, providing today (except eighteenth-century historical drawings of Bertotti and Muttoni) only graphics dating to 1970 of a single survey made by architect Soltan. This condition, in addition to the mentioned characteristics (rigour and essential form, decorative wealth) has transformed the Palladian Villa into an ideal laboratory to complete the testing of an innovative system of survey defined as “spherical panoramas” (Fangi, 2007, 2008, 2009) that has the following main characteristics: • Rapidity, economy and precision referring to the primary objective of documentation and the communication of quantity and the specific quality of palladian architecture; • coincidence of photogrammetry with photographic documentation; ease of restitution and treatment of the digital model through direct metric acquisition on spherical panoramas; Firstly there is the possibility of integrating architectural and decorative apparatus (including frescoes) through using control points of support directly acquired in the photographic documentation. The advantages to use such technique turn out to be numerous: first of all the great simplification of the photogrammetric problem: every single panorama replaces many photogrammetric takings representing a complete documentation of the object, then the high speed of execution and the easiness to plot by non-expert technicians. Then the photographic back-projection of the same panoramas used for plotting directly over the 3dimensional model, used as model texture, gives the possibility of obtaining a perfect uniformity between the geometric and photographic model. There is also the opportunity to take measurements on decorative apparatus, at the same precision of photogrammetric restitution, between 1/1000 and 1/5000 of the distance from camera to object. The back-projection is possible due to the knowledge of the orientation parameters of the panoramas. The software for the restitution has been developed in the Department. The model so obtained is exported in VRML format to be explored in interactive form through popular commercial client-software (e.g. Cortona). At the end of the communicative process a holographic model of the Villa was obtained.