Maps

Isarithmic maps, also known as contour maps, depict smooth continuous phenomena such as precipitation.  Isarithmic maps are essentially topographic or contour maps, wherein a third variable is represented in two dimensions by color, or by contour lines, indicating gradations.

Isarithmic map of temperatures on January 31, 1981 throughout the state of North Carolina

A choropleth map is a thematic map in which areas are shaded or patterned to show the measurement of the statistical variable being displayed on the map, such as population density or per-capita income.  The choropleth map provides an easy way to visualize how a measurement varies across a geographic area or it shows the level of variability within a region.

A dot density map is as a map type that uses a dot symbol to show the presence of a feature or phenomenon. Dot maps rely on a visual scatter to show spatial pattern.

The map shows the distribution and density of China's population. One tiny dot indicates 50,000 people.