ABSTRACT
This chapter describes the study areas used, and the preparation of the maps that were necessary to define the magnitude and nature of generalisation effects in different types of geographical data. It begins by providing a detailed description of the origin of the maps. The maps used were, whenever possible, obtained in digital form and, for each country, covered the same core area at the scales. The Ordnance Survey created the British maps and the Instituto Portugues de Cartografia e Cadastro, produced the Portuguese maps. An important concern in converting the paper maps into a digital form was that the process chosen was as accurate as possible and that, at the same time, would not contribute to further generalisation of the maps. Following the map transformations, the systematic error of all the maps was investigated. Systematic error, as the name indicates, is considered to be a constant error that affects the map as a whole.
