Unclassed Choropleth Map

http://go.owu.edu/~jbkrygie/krygier_html/geog_353/geog_353_lo/geog_353_lo07.html

An unclassed choropleth map is another choropleth map that portrays areal data using points, and lines, and areal symbols to depict topographic features. What distinguishes an unclassed choropleth map from a classed map is that an unclassed map isn't divided into a designated number of smaller groups and portrayed in intervals, but rather displays data using a continuous grey scale, where there can be as many intervals as areal units. The above image is an unclassed choropleth map because it uses the grey scale and the number of categories is equal to the number of data values used, not grouped into smaller numbers.