118 
Siedler, Hemmleb, Sacher 
The rectified image maps are based on a projective image transformation, which can be used, if the object surface describes 
sufficiently precise a plane. The images were processed with Eddi 2D / metigo 2D, a small, quick and efficient rectification software 
by the fokus GmbH Leipzig. While first results could already be achieved during the surveying campaign, the processing of the 
complete image maps was done afterwards. In order to achieve highest accuracy, each image has six to eight geodetic measured 
reference points, which were used in a least-squares-adjustment for the calculation of the transformation parameters. After 
processing, all reference points were overlaid with the rectified images for strict accuracy control. Because each image get it’s 
coordinate origin during the rectification, geometrical image mosaicing was performed semi-automatically. 
2.3 Unwrapped Image Maps 
For special parts of the monument, unwrapped image maps were produced. This is possible, if the object can be described with a 
parametric body. For instance, some building parts have a cylindrical shape, which allows the application of a cylindrical image 
unwrapping. We used this method for the production of image maps from all the three apses (inside and outside) and the unwrapping 
of all the three vaults. This requires an extensive surveying of the concerning building parts which allows the determination of the 
cylinder parameters and the exact unwrapping with a parametrical photogrammetric approach. We use this approach for commercial 
applications since 1996. Together with some examples it was described already earlier in literature (Hemmleb, Wiedemann 1997, 
Hemmleb et al. 2000). But within the project it was the first time, that it was used for the combination of images with different 
interior and exterior orientation parameters for the production of one image map. That was necessary because of the difficult 
acquisition conditions on the monument, which require image acquisition with different camera types. Due to the needed high 
photographical quality, beside metric images also semi-metric images with a large scale format camera were used. 
Fig. 10 shows the complete image map of the unwrapped inside of the north apse. As projection plane a cylinder with additional 
vertical profiles was derived from geodetic measurements. The upper part of the interior apse, which has nearly the shape of a calotte, 
was also projected on to the defined cylinder. Alternatively it is possible to choose a map projection for mapping of spherical shapes 
(Sacher 1999). Fig. 9 shows the large scale format images, which were used for the unwrapping of the interior apse. 
Fig. 9: Large format images of the interior north apse 
For the unwrapping of the outside altogether seven images were used, which were taken with UMK 10/1318 and Cambo Wide 58. As 
projection plane also a cylinder was used. The resulting image map is shown in Fig. 11. Brightness and contrast differences result 
from difficult acquisition conditions and the restricted time schedule, which did not allow to wait for cloudy weather. 
As already mentioned, the three vaults of the still existing north nave were also unwrapped. The view into one of the three vaults 
from the ground (Fig. 2) gives an idea of the great demands on the photographic quality for the needed images. One of the used three 
images is shown in Fig. 4. The resulting image maps are referenced to the global three-dimensional geodetic coordinate system. 
Beside documentation and mapping purposes they were used for investigations of the building geometry, technical and static 
problems. Fig. 12 shows the unwrapped image map of the middle vault.