Dasymetric Maps

Dasymetric mapping is a cartographic technique with roots in choropleth mapping. Both techniques originated in the 1800s when cartographers and others began to design maps of population distributions. Like the choropleth map, the dasymetric map uses area symbols to show variations in topics collected by standard political units (e.g., census tracts, county boundaries). The advantage of this particular representation lies in its treatment of the boundaries of the political units. A choropleth map of county population density, for example, would suggest uniform densities within each county, with possible abrupt changes occurring between adjacent counties due to the geography's artificial nature. The mapping of the topic with this technique is heavily influenced, then, by the geography of the political units used; displaying population densities by census ...