Thematic Map

Synonyms

Chart; Data map

Definition

The graphical representation of quantitative data or qualitative data for a given geographic area (e.g., regional unemployment rate or type of crops grown).

The many different methods that cartographers apply to create thematic maps are used to define a thematic map more precisely. The following five are found most often:

• 1. Choropleth maps. In choropleth maps, the areas of the map are shaded or patterned in proportion to the value of the data to be displayed for a particular area.

• 2. Dot maps. These maps use equal sized dots to show the presence of a feature at a particular geographic location and thus display spatial distributions. A dot need not be restricted to a single occurrence; it may indicate any number of entities.

• 3. Proportional symbol maps. When drawing proportional symbol maps, a cartographer selects a symbol (e.g., a circle or a bar), places it at the spot on the map to which the data apply, and varies the symbol’s size from place to...