How big is Greenland really? Your map may be misleading you

President Trump is again raising the idea of ​​annexing Greenland, the semi-autonomous Arctic island that is part of Denmark.

Greenland’s location between North America and Russia gives it strategic value for the US, which already has a military base there. “We absolutely need Greenland,” Trump said on Sunday. “We need it for the defense.”

If all this talk makes you want to look at Greenland on a map, you might notice its size. Greenland is the largest island in the world and covers more than 836,000 square miles.

But is Greenland really as big as it seems on the map? It turns out it depends on the card.

Although globes provide a fairly accurate picture of the world’s geography, things get a lot trickier when you try to represent a sphere on a two-dimensional surface. The shapes and sizes of land masses can become distorted, and distances and directions threaten to become shaky. There are many different ones types of world mapsand each has its strengths and weaknesses.

One of the most common card types is the Mercator projectionnamed after the 16th century Flemish cartographer who invented it. This is the one you might have seen in an atlas as a kid, and a version of it is used in online mapping tools such as Google Maps.

Mercator’s map takes the Earth’s latitudes and longitudes (parallels and meridians) – which curve around the spherical sphere – and turns them into straight lines.

This allowed sailors to plot a course between any two points using a straight line, but it also caused distortions on the map as you got further from the equator. Greenland for example seems about the same size like the continent of Africa on a Mercator map, even though Africa is about 14 times larger.

“Mathematical [the parallels and meridians] are pulled apart, pulled in different amounts and sizes from the equator to the poles, so you get this kind of exaggerated effect, if you will, at the higher latitudes where land masses appear enormous,” said Fritz Kessler, a geography professor and map projection expert at Penn State.

There have been organized efforts to move away from the Mercator projection and use alternatives that provide a more accurate picture of relative country size. The Robinson projection, which attempts to better balance the sizes and shapes of land masses, attempted to solve the “Greenland problem.” And last year, the African Union supported an effort to replace Mercator with the Equal Earth map, which better reflects the scale of the continent.

But which of the many map projections you choose at any given time really depends on what you’re using the map for, according to Kessler.

‘Will it be used to measure distances or directions? Corners? Areas? Show distributions of thematic data, you know, population?’ he said. “There are hundreds of projections that can be used, and the fact that we’re focusing on only a very limited subset I think is another issue that needs to be addressed.”