DTM's and DEM's are widely used for landscape reconstruction and GIS analysis. Very accurate models are possible to construct on a small scale with the aid of a 3d-scanner, or on a larger scale with the aid of photogrammetic processing of aerial images. But far more often archaeologists will have to rely on software to process point-data and contour lines.
The different kinds of software have many algorithms and parameters. They have to be used with care, as changing an algorithm or the parameters for an algorithm, will dramatically alter the resulting DTM or DEM. Especially if the model is used for further GIS analysis, any lack of knowledge on these differences may have serious repercussions on the conclusions of for instance site-locations and ways of communication.
Ken Kvamme already demonstrated these possible dangers almost a decade ago. Since then, many new and more elaborate algorithms came available, capable of both creating a better model as well as an even more distorted image of reality. This suggests that archaeology may benefit by an update on this subject.
Key words: DTM, DEM, GIS, Slopes, Cost-analysis