THE MULTI-IMAGE SPHERICAL PANORAMAS AS A TOOL FOR ARCHITECTURAL SURVEY

The surveys of the interior of two churches in Italy, the Magdalene’s church in Pesaro, and San Dominic church in Arezzo, are shown and described as examples of a new photogrammetric technique. The first church is one of the most noticeable baroque architecture in the Marche region and it has been designed by the famous architect Luigi Vanvitelli in 18 th century, the second one is a large and simple church in Arezzo. The proposed technique is based on the multi-image spherical panoramas. For the formation of the plane image of the spherical panoramas the commercial software has been used. The spherical panorama can be regarded as the analogical recording of the angular observations of a theodolite having its center in the center of panorama. But to be set in operational conditions as a theodolite, the spherical panorama has to recover two rotation angles to set the verticality of its principal axis. The estimation of such rotation angles can be performed both in a preliminary phase prior to the plotting or in a unique phase in a block adjustment. Control points, control directions, geometric constraints such as verticality and horizontality of space lines, can be used. In these study-cases almost no one of such control information was necessary, but the only block adjustment was sufficient. The block adjustment finally furnishes the estimation of the unknown points coordinates together with the six orientation parameters per panorama, three translations and three rotations, by means of the known geodetic equations of the horizontal direction and the zenith angle, (modified to take into account the two horizontal correction angles), that are nothing else than the collinearity equations of the spherical panoramas. The technique of the spherical panoramas has previously been experimented and used for the survey of two of the most noticeable Italian squares, Piazza del Popolo in Ascoli Piceno and Piazza del Campo in Siena. By that time, to be able to use the panoramas, besides the angular corrections, further polynomial corrections were necessary, gotten from a dense network of control points (100-200), (Fangi, 2006). In the case under examination not only such corrections were not needed but also no control point was used. The procedure improvement can be explained with the shorter distances, with the good improvement of the Stitching software, (that thanks also to the ceiling texture, produced better panoramas), and finally with the improvement of the adjustment algorithms, via the block adjustment. The image distortion is automatically corrected by the software itself in the rendering phase, by merging the overlapping image frames. The interior orientation is skipped. For the time being, the final plotting accuracy is limited by the quality of the panoramas and by the resolution of the spherical images. In the shown examples the width was 10000 and 15000 pixels for all the panoramas, corresponding to an angular accuracy of 0.04-0.03 g, therefore very scarce. The 3d plotting was performed with monoscopic multi-image observations. In the first example the block adjustment supplied, besides the orientation parameters, the coordinates of about 600 points, observed in at least three panoramas. The achieved accuracy is in the order of few the centimetres say σx = σ y = ±0.02 m and σz = ± 0.03m. The advantage of the spherical panorama in comparison to classical photogrammetry consists in the greater completeness of the information due to its 360° amplitude, giving a synoptic view of the whole environment. A single panorama can replace many image frames; a couple of panoramas can substitute many photogrammetric models. The spherical panoramas are very simple, fast and easy to realize, they are very economic, and they are a very useful and powerful tool for the documentation and survey of the cultural heritage. The present research has been financed in a Firb National Project, THE GEOMETRICAL SURVEY FOR THE CONSERVATION OF THE CULTURAL HERITAGE IN DEVELOPING COUNTRIES