(Regierungspräsidium Stuttgart/Landesamt für Denkmalpfelge Baden-Württemberg, Germany)
Abstract: This contribution introduces a slightly older project which, however, has triple relevance for this year’s conference – in terms of the overarching theme of urban archaeology, for pre-excavation strategies and, in the technical execution of the project, especially for the session “Georeferencing historical maps”.
In 2002 in Petershausen quarter of Konstanz South West Germany planning permission was granted for a large new communal administrative building within the area once occupied by ancillary buildings of the Benedictine Abbey Petershausen, founded 992. An excavation was planned and in preparation, historical plan material was examined. Exceptional in this respect is the plan of Petershausen by the then “Master of City Buildings” (Stadtbaumeister) in Konstanz the Austrian architect Peter Nenning. The survey was carried out and the plan drawn at time of the Napoleonic secularisation, as part of an inventory to accompany the transition of the buildings from the Benedictine order to the Grand Duchy of Baden.
Then plan shows a collection of buildings varying in date from medieval to the late barock. In the south-western area of the plan, where the excavation was planned, long disappeared buildings are shown. The question arose as to whether the plan is a useful and accurate historical source? Could it help us as a non-intrusive prospection tool in the forefront of the excavation and provide us preemptively with important details allowing a more targeted Excavation?
This contribution attempts to answer these questions. Using a combination of standard CAD and rectification software Nennings plan was georeferenced according to today’s topography – a task which turned out to be much more difficult than originally expected. A whole series of other later historical maps had to be found to bridge the gap as “stepping stones into the past” and were integrated into the project. A project which turned into a fascinating discourse between the ordered world view of a late Rococo/early Biedermeier architect and today’s real, considerably less rectangular topography. And with the dig that followed it was possible to test the method as a soft prospection method against the actual excavation results.
Keywords: georeferencing, prospection, pre-excavation, historical plans