DOCUMENTATION AND DEVELOPMENT OF THE COLUMNS OF THE CHURCH OF ST. CHARLES IN VIENNA

The Church of St. Charles in Vienna is flanked by two huge columns. Both are decorated with a relief showing different scenes of St. Charles Borromaus and are due for restoration work in approximately spring 2006. This paper presents how these two columns and their relief can be reconstructed from photogrammetric measurements. First in a bundle block adjustment all photos and control point measurements are used simultaneously to derive the photo orientations and the defining parameters of the columns' surface (e.g. a cylinder). Afterwards the columns' surface is developed and the texture from each photo is transferred into the geometry of this development. This result corresponds to an ortho-photo of the developed column surface, which will be used several times in the restoration phase: for documenting the current state of damage, for supporting the financial calculations of the companies who are interested in taking over the restoration work (as this work will be contracted out) and finally for the restoration work itself, as the working restorers of the authorized company are obliged to record all their work precisely in this ortho-photo. In order to achieve the required high resolution of 1mm on the entire column (size: height 40m, diameter 5m) in this ortho-photo, the arrangement of the cameras has to be planned in detail. After completing the restoration work the post-restoration state of the columns will be surveyed again using photogrammetry. This way not only the consistent documentation of the historical evolution of the building material is guaranteed, also a quality control of the restoration work is possible by comparing the pre- and post-restoration states with the recordings of the restorers.