Unraveling the categorical bias in historical cartographic material - as data for landscape research

Data specifically produced for use in landscape research and for environmental monitoring purposes is a new phenomenon and consequently historical cartographic material are often utilized in the analysis of landscape change, land use and land cover dynamics as well as assessments of environmental and cultural aspects of the landscape. However, the extensive reliance on historical cartographic data is not reflected in research on the reliability and precision of the data.Maps are generally produced in order to provide a spatial model related to a particular social need or utility, identified by the individual or organization ordering the map. The cadastral maps produced by nation states to collect revenue and the topographic maps made for military purposes in most western countries, are good examples of the result of such socially and historically situated map making practices. Thus maps have a constructivist character and should not be viewed as objective representations of the world, but ratheras categorizations of the landscape, derived to produce data related to specific societal processes. This paper investigates the nature of different forms of cartographic categorizations of the landscape in Denmark during the last 200 years. Three different cartographic representations of the landscape are included; (1) Cadastral maps, (2) Topographic maps and (3) Environmental maps. These map types are evaluated in a comparative analysis of the way they represent the landscape, in order to analyze their different categorical bias. The consequences of the differences between the three forms of cartography will be discussed, suggesting a need for the development of methods and procedures for using historical cartographic data, especially to create links between former economic and military categories of the landscape to categories which comply with data used today. It is discussed how an improved understanding of biases inherent to historical cartographic sources may advance the study of processes of landscape persistence and change