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Maps of the Census: a rough guide
Jason Dykes & David Unwin
Department of Geography, University of
This Case Study describes the considerations that are needed to produce maps of data from the Census of Population. The `area value' or choropleth map is the standard means of displaying such information on paper. It is a very imperfect visualisation device. First, it is necessary to be careful about the numbers that are mapped and, in particular, never to map absolute numbers. Second, choropleth maps are very sensitive to the mapping zones being used. To produce maps that do not distort the underlying distributions it is necessary to understand how the zones were defined and the effects of their varying sizes on the mapped pattern. Third, there are a series of strictly cartographic considerations related to how these maps are classed and the symbolism used. All of these issues are illustrated using data from the 1991 Population Census for Leicestershire, UK.
These problems lead to a consideration of the need to develop new mapping tools. Dynamic maps can take advantage of an interactive software environment to overcome some of the limitations of the static map. The possibilities which they provide for interactive engagement with data make them appropriate tools for exploratory analysis, or visual thinking. A mapping tool is introduced, which exemplifies this form of map use and examples of the techniques that might be used to visualize the UK Census of Population are provided.An annotated bibliography is provided to refer map makers and users to relevant literature.
Graphics Multimedia Virtual Environments Visualisation Contents