Investigating land area categories in largescale historical topographic maps in relation to analysing landscape change: From 19th century military assessment of landscape trafficability to 21st century land use and land cover categories

Analysis of historical land use and land cover change (LULCC) of pre-1950s landscapes primarily relies on cartographic documents as the source of spatially explicit infor-mation. Methodologically, most historical LULCC studies utilizing historical carto-graphic documents report on the geometrical precision and correctness of georeferencing and vectorization. However, often less attention is devoted to careful interpretation of land area categories. Thus, information in historical maps is taken for granted or seen as self-explanatory. This paper presents an analysis of land area categories in Danish histor-ical large-scale topographic maps from the second half of the 19th century in relation to a recent research project focused on the development of automated methods for vectori-zation of historical maps. The analysis reveals that the classification of land area catego-ries is complex and that categories in the legend cannot necessarily stand direct compar-ison to modern LULC categories. Despite a similar appearance (i.e. sharing the same name as categories in current official geo-data), the categorization of land in the maps discussed here originally rested on a military oriented assessment of landscape traffica-bility. This result implies that thorough analysis of categories in historical maps is need-ed if data are to be used for LULCC studies. Thorough historical analysis of the devel-opment of the mapping and representational practices of land area categories in histori-cal maps can reveal both a more consistent understanding of the relationship between map categories and the historical LULC, but it can also assist the development of auto-mated methods for extracting vector data.