Measuring on a map · 4 min
Why maps lie about size
How flattening a round Earth makes Greenland look like Africa, and which maps tell the truth.
Measuring on a map
You can't flatten an orange peel
The Earth is round and a screen is flat. Every flat map has to stretch, squash or tear the surface somewhere. The rule that does it is called a projection.
No projection gets everything right. Each one chooses what to keep true, such as shapes, areas or directions, and gives up the rest.
Lesson notes
Everything from the cards above, on one page to come back to.
You can't flatten an orange peel
The Earth is round and a screen is flat. Every flat map has to stretch, squash or tear the surface somewhere. The rule that does it is called a projection.
No projection gets everything right. Each one chooses what to keep true, such as shapes, areas or directions, and gives up the rest.
Mercator, the map you see every day
Most web maps, including Google Maps, use a version of the Mercator projection. It keeps the shapes of small places right, which is perfect for zooming into streets.
The price is size. The farther from the equator, the more Mercator blows things up. Near the poles it stretches without limit, which is why web maps stop at about 85° north and south.
Maps that keep size true
Equal-area projections keep every country's size in the right proportion, at the cost of squashed shapes near the edges. Equal Earth, from 2018, is a popular modern one.
MapGO's world map in its farthest-from-the-sea study uses Equal Earth for exactly this reason: so no region looks bigger than it is.
Measuring is safe, looking is not
MapGO measures distances and areas on the curved Earth, not on the flat picture, so a figure it gives you is right even on a Mercator map.
Your eyes are the problem. When you compare sizes by looking, remember the map is stretching everything far from the equator.
Questions
Why does Greenland look so big on maps?
Most maps use the Mercator projection, which enlarges areas more and more towards the poles. Greenland is far north, so it is drawn many times bigger than it is.
Which map projection shows the true size of countries?
Any equal-area projection, such as Equal Earth, Mollweide or Gall-Peters. They keep areas in proportion but bend shapes.