The CIPA(Comité International de Photogrammetrie Architecturale) directive

The traditional graphic survey and the photogrammetric survey differ essentially because: - the first provides a graphical representation in scale, and a series of photographs, which offer a mono spatial vision, but do not allow measurements to be taken; - the second, thanks to a pair of frames, offers a stereo spatial vision and allows to detect the measurements of the photographed objects. In practice, photogrammetric offers the spatial coordinates (x, y, z) of each point represented on the pair of frames. When it is not considered sufficient to detect the measurements directly from the stereo image, the so-called restitution is carried out, even after years, that is, a graphic representation, through which only two coordinates are recorded for each point chosen in the photograph: - x, y for the plan representation; - x, z for the representation in elevation. It goes without saying that the return only makes sense if "finalized", requiring a choice of points according to a specific purpose, with a time (and, therefore, a cost) proportional to the elements represented.

The proposal, consisting in the establishment of an international archive of photogrammetric surveys of monuments subject to risk of destruction, perhaps appeared utopian half a century ago, both because of the use in photogrammetry of glass plates, which are difficult to duplicate and transport, and for the existence of optical-mechanical restitutors, who accepted only frames of cameras with well-defined format and focal length. Today all the genius of the idea emerges, since, with the use of digital photography, all the problems of archiving and restitution have disappeared.

The proposal, consisting in the establishment of an