A to Z GIS | Explore this related guide, featuring updated terms and graphics and developed in coordination with Esri’s GIS Dictionary team.
Learn more about A to Z GIS
GIS Dictionary
Browse dictionary
isoline
URL copiedShare URL
[symbology]
A line that connects points of equal value for a specific variable on a map, such as elevation, temperature, or pressure. Isolines fall into two classes—isarithms, in which some values actually exist at points, such as temperature or elevation values—and isopleths, in which the values are ratios that exist over areas, such as population per square kilometer or crop yield per acre. Isolines are used to illustrate data ranges that show trends and gradients.