These thematic maps use a variety of cartographic symbols to depict the spatial pattern of a particular geographic quality or quantity .
In 1854, John Snow, a doctor from London created the first thematic map used for problem analysis when he mapped cholera's spread throughout the city.
Thematic maps emphasize spatial variation of one or a small number of geographic distributions. These distributions may be physical phenomena such as climate or human characteristics such as population density and health issues.
Thematic maps are used to display geographical concepts such as density, distribution, relative magnitudes, gradients, spatial relationships and movements.
* They provide specific information about particular locations.
* They provide general information about spatial patterns.
* They can be used to compare patterns on two or more maps.
There are five types of thematic map that are particularly useful to decision makers, analysts, storytellers, and others who are looking to draw insights from their data, tell a powerful story, or gain a greater understanding of the world around us. They are choropleth map, isopleth map, proportional symbol map, dot map and chorochromatic map. In this unit, let us learn about dot map and choropleth map in detail.