Isopleths

Isopleths are lines drawn through areas of equal value. These lines can be used to correlations between objects being studied. If you noticed a steady and erosion of a particular rock on the east coast you could then use isopleths to draw the correlation between the sane rock and erosion on the west coast if it weer occurring at similar rates. This map shows concentarations of TCE trichlorolethlylene in a river in Kentucky.

Link: http://www.stonelions.com/Dayhoit.htm