Computational approaches towards the understanding of past boundaries: A case study based on archaeological and historical data in a hilly region in Germany

Abstract Boundaries at different scales or in different cultural contexts vary in permeability, fuzziness, and continuity. The contribution of methods from the Geographical Information Systems (GIS) toolbox used in archaeology for the understanding of boundaries is explored in a case study based on known boundaries that are located in a hilly region east of Cologne, Germany. The known political and religious boundaries date back to the 16th and early 17th century. Furthermore, a linguistic boundary traversing the study area is well-known. A classification of the reliability of the political boundaries is presented based on evidence from different sources including archaeological sites. A traditional GIS method for delimiting territories is Voronoi polygon generation, also known as Thiessen polygons. A variant uses least-cost distances, accounting for costs of movement. A site catchment of a settlement consists of all locations that can be reached by expending a given cost limit. Both the initial Voronoi computations as well as the site catchments failed to reconstruct a significant proportion of the known past boundaries. Therefore, the association of the known boundaries with rivers, ridges, and modern parish boundaries was tested and found significant. In contrast, poor soils and voids identified by least-cost Kernel Density Estimation (LC-KDE) of 16th century settlement locations are no preferred locations of past boundaries. Boundaries of Voronoi polygons based on modified cost models taking the association of past boundaries with ridges, rivers, and modern boundaries into account reconstructed about 27 % of the confirmed past political boundaries successfully. The association of the linguistic boundary with the features mentioned above is insignificant. Diagnostic place names are the traits forming the basis of Voronoi diagrams and LC-KDE applied in archaeological studies for reconstructing boundaries. Considering the uneven distribution and fairly low number of traits, the results of these two approaches are satisfactory.