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Isoline Maps

In geography, it is often necessary to explain information with a map. Let’s consider an example that most of us will remember seeing. Have you ever seen the weather report on your local news? One of the jobs of a meteorologist is to show us the temperature. They do this by looking at images called isoline maps. 

An illustration of an isoline map made to show temperatures.

An example of an isoline map you might see on the weather, showing the temperature.


What are Isolines?

Isoline maps contain isolines. These are lines that represent things that have the same (“iso-“) value. That could be anything from height to heat, as we said in our weather example.
In the example, the weatherman will use isolines to show differences in heat between areas. The hottest areas are often red, the warm areas yellow, and the cold areas blue. Isolines are useful because they quickly let you know what you’re looking at. It’s very easy for you to understand what they are telling you.

An image of a topographical map made with isolines.

An example of a topographic isoline map.

One area in which isolines are especially important is mapping global temperature. As the Earth warms, we need to keep track of which places will be most affected. They tend to be those closer to the equator (in desert-type biomes).

Types of Isolines

In addition to weather, isolines can also describe any other type of data. For example, a population map can use isolines to tell us where all of the human beings are around the Earth.
Some isolines have names. The following list names a lot of commonly used isolines, but it is not all of them. 
  1. Isotherms show areas that have the same temperature.
  1. Parallels show places that are at the same latitude. 
  1. Meridians show places that are at the same longitude. 
  1. Isobars show areas under the same atmospheric pressure. 
  1. Isobaths show places that are at the same depth underwater. 
  1. Contour lines show places that have the same height on land. 
  1. Isohyets are isolines that show places with the same amount of rainfall over a given period of time. 
Population density isoline map.

This Isoline map shows population density.

Other Great Resources

Penn State on Isolines: https://www.e-education.psu.edu/geog486/node/1873

The Different Types of Isolines – ThoughCo: https://www.thoughtco.com/what-are-isolines-4068084

(Video) Drawing Isoline Mapshttps://www.youtube.com/watch?v=KY8BjrTw5Lg



Written by: Sylvia Choo