Isoline maps

http://regentsprep.org/regents/core/questions/questions.cfm?Course=ESCI&TopicCode=07

Isoline maps use lines, continuous, to show areas with equal values for a given them. In this example the isolines are used to show precipitation. The area that runs along the line add equal amounts of precipitation. Isoline maps have a lot of uses within the realm of thematic mapping and are used to show continuous data, unlike choropleth maps.