The isarithmic or contour map uses isolines to depict continuous values like precipitation levels. These maps can also display three-dimensional values like elevation on topographic masp. Generally data for isarithmic maps is gathered via measureable points (e.g. - weather stations) or is collected by area (e.g. - tons of corn per acre by county).
A map of Ohio’s maximum average high temperatures in 1971-2000 with red being the highest and blue the lowest.
The chloropleth map uses graded differences in shading or color or the placing of symbols inside defined areas on the map in order to indicate the average values of some property or quantity in those areas.
Percentage of individuals living in poverty, by county, 2000.
A dot density is another type of thematic map and uses dots to show the presence of a theme and display a spatial pattern. On these maps, a dot can represent one unit or several, depending on what is being depicted with the map.
This map shows the density of the population in 2000, with each dot representing 10000 people.