In this module we are concerned with the representation of data values by the form of thematic mapping known as choropleth mapping.

What is a choropleth?

The choropleth map is a cartographic representation employing distinctive colour or shading applied to areas, which can be administrative or statistical.

• Both aggregated and bounded, areal, classified data are mapped.

A choropleth map may be seen as a 3-D histogram or stepped statistical surface. The image at the top right of this page shows the stepped statistical surface for a demographic variable for Perth post codes.

The choropleth map is a planimetric representation of this 3-D data model. The map at the bottom right shows a choropleth map derived from the data modelled in the surface shown at the top right.

• Data shall be collected by statistical or administrative areas.
• Area symbol classes are selected to represent range-graded numerical classes.
• Symbols are applied to areas on the map whose data fall into the symbol classes.

Is any data suitable for choropleth mapping?