ISOPLETH MAPS
An isopleth map generalizes and simplifies data with a continuous distribution. It shows the data as a third dimension on a map, thus isopleth maps are more common for mapping surface elevations, amounts of precipitation, atmospheric pressure, and numerous other measurements that can be viewed statistically as a third dimension.
The third dimension is shown by a series of lines called isopleths which connect points of equal value. The isopleth interval is the difference in value between two adjacent isopleths. Note, the values of the isopleths drawn on the map are ALWAYS multiples of the interval. Isopleths never cross or divide and always form enclosed circles, however, this occurrence may not be in the mapped area.