Cartographic Representation of Dresden’s Historical Development by Projecting a Movie onto a Solid Terrain Model

On the occasion of the 800th anniversary of the first mention of the city of Dresden (Germany) a new exhibition for the local City Museum was designed. The intention of the exhibition's concept was to use modern and innovative exhibits to attract a broad audience. A key element of the exposition is a 2.00 m by 1.50 m solid terrain model of the Dresden Elbe valley. A film, which shows the development of the depicted region since the year 8000 B.C. is projected onto the terrain model by a video projector and the help of a tilted mirror. This true 3D installation is one of the first of its kind worldwide. It facilitates much more thematic flexibility than terrain models without changing illumination. Both the terrain model and the film result from a cooperation of the City Museum of Dresden with the Institutes for Cartography and for Software- and Multimedia-Technology of the Dresden University of Technology. The scale of the solid terrain model is 1:16,250. It is four times vertically exaggerated to improve the perceptibility of small terrain features for the visitor. The projected film is a FlashMX animation, for which several tenths input data layers were prepared with the GIS software ArcGIS and the vector graphic software Freehand. Input data for both the solid terrain model and the animation were Laserscanning DEM data and ATKISDGM/- DLMdata. A major challenge of the terrain model construction was the reconstruction of the primordial terrain. As the input data showed the contemporary situation of the terrain a significant number of visible anthropogenic terrain changes, such as bridges, railway lines, motorways and man-made riverbeds had to be removed. An iterative semi-automatic approach was developed, which cuts relevant areas from the data and using a linear TIN interpolation that filled the data holes afterwards. The filtered data set was cut into a polyurethane pattern plate by using a Portatec milling machine by the Institute for Production-Technology of the Dresden University of Technology. In a stepwise process an accuracy of 1/100 mm in the three dimensions x, y and z was reached. Afterwards the solid terrain model was varnished with a special white colour, for which previous tests had shown optimum reflection behaviour.