What is a thematic map?

About maps Making maps

There are many types of maps. Maps have been designed with specific uses in mind since the earliest cartographers began mapping earth centuries and centuries ago.

Ancient Mercator Map

Planisphere by Rumold Mercator 1587

In fundamental ways maps began as a means of understanding the lands and waterbodies that comprised the world, charting exploration and discoveries of previously unknown places, and defining a nation's imperialistic extents.

Map of ancient Germany by Edward Wells

Map of Ancient Germany - Edward Wells 1700

Over time maps have changed and expanded the way we interpret information about what happens all around us. Maps that display a singular topic are known as thematic maps.

A thematic map focuses on a specific subject

This could be anything from highly statistical information such as population growth, distribution, and demographics; rainfall amount over time in a specific location; the distribution of award winning children's book illustrators; or the touring route of your favourite band.

A map showing the distribution of Caldecott Medal Winners Across America. Cartography by Where Exactly Maps

This example shows the distribution of children's book illustrators who have won the Caldecott Medal in the United States.

Thematic maps are designed to highlight and reveal the subject's information. This means the geographic features on a thematic map are tailored to reflect or best support the map's theme. Where you might see 12 lakes on a regional map, a thematic map of the same area may simply show the 3 largest. In this way more space is available to show information directly relating to the subject of the map. It improves the overall clarity without losing the important backdrop the topography provides.

Types of thematic maps

Within the sphere of thematic maps are a variety of types. Depending on the information being displayed, using a particular cartographic technique can communicate more effectively. The following examples are primarily used to symbolize statistical data. A thematic map exploring a complex subject may incorporate several key-maps using a few of these to provide an enhanced understanding of the subject.

Choropleth

Uses a colour gradient to show quantitative information within distinct boundaries. These could be population by municipality, or census division, or in this example, by a country's estimated population.

Graduated Symbol

Graduated symbols are used to represent size relationships and compare quantitative data. Here, the population of large cities across the world are symbolized based on the number of people living in each place. It's easy for a user to see the comparative sizes of each.

Dot map

This type of thematic map uses simple dots as a representation of a numeric value. Each dot here represents 7 million people.

 

Isarithmic

These types of thematic maps are used to represent data such as temperatures [isothermal], rainfalls [isohyetal], weather patterns and things like atmospheric pressure [isobaric]. This type of data does not  follow or adhere to geographic boundaries and therefore has an overall more generalized appearance.

Thematic map showing isopleth example in temperature increases

The beauty of thematic maps

Thematic maps are some of the most beautiful and captivating maps ever made. Because they delve into a focused idea, the artistry of the cartography and additional map elements are usually much more exciting and appealing.
Anyone who has had the pleasure of beholding the specialty maps published by National Geographic will agree that they are among the finest examples of thematic maps ever created.



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