Isopleths

An isopleth is described as a line on a map that shows equal values of an area. A good example would be a map of the Gulf of Mexico. There are contour lines on maps of the Gulf of Mexico that show fisherman, boat captains, and the public in general exactly what the depths are in a given and by doing this, we can see the different bottom areas of the Gulf of Mexico that have equal bottom depths. There are areas south of Tallahassee in the Gulf of Mexico that have equel depths and they would be shown via isopleths.

http://www.nature.nps.gov/air/edu/lessons/figure3.cfm