Measurement image documentation of all outer walls of the former keep and prison. The difficulty was to consistently grasp approximately 20 m high wall surfaces in a way that was correct for the deformation. The documentation was corrected to scale in 1:50 scale in four photo sheets of 30 x 45 cm format. The recordings were made analogously in the format 6 x 9 cm, scanned and digitally processed. At the same time, measuring points on the object were recorded with a digital measuring station and stored in a database. This database serves as the basis for the digital equalization process. The processing period was eight working days and was carried out in cooperation with the historical-building researcher Peter Knoch.