Isopleth map

http://content.cdlib.org/xtf/view?docId=kt4j49n6r5&brand=calisphere&doc.view=entire_text

There are many different kinds of contouring maps and this isopleth map is one example of a map that uses the ideas of contouring to "connect" data to show a specific pattern. This map presents information that is shown about the different amounts of harmful chemicals that are found throughout the San Fransisco Bay area. From the changes that were collected and plotted throughout the several months, researchers were then able to use the isopleths to infer possible sources of the pollution and solutions for the clean-up of the chemicals within the water. This isopleth map is one example of how contouring lines are really able to show a change and of a specific characteristic in a location and to what extent it increases and decreases.