Ronny WEßLING / Jakob MAURER / Alexandra KRENN-LEEB
(Department of Prehistoric and Historical Archaeology University of Vienna, Austria)
Keywords: structure from motion, documentation, pole aerial photography
By the use of archaeological standard equipment (measurement unit and camera) structure from motion approaches offer an affordable, easy to use and accurate documentation method for stratigraphic excavations. However, it is still not applied in a frequent and systematic way.
In the well preserved Late Neolithic settlement Kleiner Anzingerberg/Meidling im Thale in Lower Austria structure from motion has been used intensely for single surface documentation. The commercial software Agisoft Photoscan was applied for fully automatic calculation of intrinsic and extrinsic camera calibration parameters, for creation of three dimensional point clouds and for generation of photorealistic surface models using multi view stereo algorithms. The models have been transferred to a GIS environment which is used for visualization and data management purposes. By arranging and displaying the models according to their stratigraphic positions a four dimensional virtual reality is created through which the user can move interactively. Thus this method of digital preservation allows an objective and verifiable documentation of archaeological remains, which makes them an excellent basis for further interpretation.
To receive accurate results special attention has to be paid to the process of data acquisition: next to high image quality and good light conditions high stereo coverage of the images is obligatory. To achieve this, ground based aerial photography was put to use at the site Kleiner Anzingerberg. A photo crane and telescopic pole served as camera platforms for the generation of serial vertical and overview shots. Images that have been taken in this way can improve the accuracy and point density as well as the computing time required to build the models.