(Oxford Archaeological Unit Limited, UK )
Archaeological stratigraphy is a complex phenomenon that encompasses notions of gradual and abrupt change, driven by physical and biological agents on different spatio-temporal scales. To fully understand a site’s stratification processes, archaeological evidence frequently has to be integrated into a wider framework of data and theory contributed by soil science, biology, geomorphology and even geology.
The real complexity of stratigraphy continues to make our best excavation planning, recording and analysis schemes seem inadequate. That this also holds true for our digital tools seems bizarre, given the obvious usefulness of computer technology for managing and analyzing voluminous, heavily structured stratigraphical information.
For many years, the Harris Matrix and its underlying idea of “interfaces” have been providing a sound way of structuring the observable, topological relations between features that many archaeologists would probably consider to be the backbone of stratigraphy. Such information is easily representable as database tables or mathematical graphs and some software tools have emerged to create and manage Harris Matrices. Among these, Irmela Herzog’s Stratify software stands out for incorporating innovative methods of stratigraphic visualization and inference.
However, the Harris Matrix is just one important derivative of a site’s stratigraphic record, it does not equate to full stratigraphic information. For the derivation of other, perhaps equally important, components that can help us understand site formation processes, we must invoke alternative representations of stratigraphic units such as GIS voxel models. An attractive option is to extend current open source GIS technology, enabling it to handle a range of stratigraphic components and representations — preferably in 3D, as close to the physical reality as possible.
Unfortunately, there is a lamentable absence of basic requirements that needs to be overcome first: stratigraphic extensions to geo-data formats, symbologies, visualization techniques and data model specifications are all sorely missing. Nevertheless, current GIS systems are increasingly capable of managing three-dimensional datasets and the paper will explore some of the more promising developments towards stratigraphically enabled GIS technology.