Methodological approach to 3D documentation of excavation processes


Every archaeological site has its specific and unique stratification defined by the sequence of single deposits and special surfaces (interfaces) i.e. the units of stratification. The stratigraphic excavation process recovers the discernible units of stratification in the reverse order of their deposition or creation. During the excavation process the stratification is irreversible destroyed. Therefore each excavated unit of stratification has to be documented in the most accurate way in three dimensions. Furthermore these units have to be aligned within the stratigraphic sequence (Harris Matrix) following the rules of archeological stratigraphy. To gain a complete reconstruction of the site, the surfaces of the excavated deposits and the specific surfaces of pits, ditches etc. have to be documented in 3D. Such complete 3D recording is accomplished by the developed method called “single surface planning”. The three-dimensional extent of any single deposit is defined by its surfaces consisting of a top and bottom surface, as revealed sequentially by the stratigraphic excavation process. Together with the special surfaces or interfaces of pits, ditches, walls etc. the basic elements for a complete 3D documentation are surfaces. Their complete documentation demands accurate and efficient methods for 3D single surface recording, analysis and archiving. Recent developments have proven that terrestrial 3D laser scanning (TLS) and image based 3d modelling (close range photogrammetry) are suitable methods in terms of recording. For further archaeological analysis and archiving strategies GIS-based approaches offer a broad range of opportunities and advantages. After the development of a GIS-based procedure for the digital documentation of the stratigraphic excavation process we started to test and standardize the use of 3D Laser Scanners (Riegl LMS Z210i, Z360, Z420i and newest VZ 400) combined with digital imagery extensively to implement this technique into the daily archaeological work-flow. Recent research focused also on image based 3D modelling. With this paper we want to present and discuss the recent results of the use of a standardized GIS-based method for high resolution and complete 3D-recording of an archaeological stratification.