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choropleth maps — English
Thematic maps on which the spatial distribution of certain variables are quantitatively represented by means of colours or shadings within the boundaries of geographical units that are actual administrative units such as farms, districts, suburbs, countries or even continents (see “thematic map”, “cadastral map” and “topocadastral map”). An explanation (or key) that indicates what each colour represents is essential to read the map. Choropleth maps are one of the most often used types of maps in Geography, but they have some disadvantages which geographers must always bear in mind. The main disadvantage or limitation is that intra-areal spatial generalisation (a form of spatial generalisation) within administrative units is used (see “spatial interpolation”, “interpolation” and “extrapolation”) which could easily convey a spurious spatial image. The National Geographic Magazine which is the most widely read geographical publication and is mostly read by non-geographers and lay readers, very often uses choropleth maps. The lay readers are not able to analyse the generalisation these maps entail and cannot appreciate the pros and cons of the use of these maps. Fortunately, the National Geographic Society is scientifically totally sound and geographically highly respected and will not publish a map that could convey incorrect or misleading information.
