How does Mercator projection work?


I mean is stuff bigger than it actually is, or do things seem more stretched out? I am confused. I would be delighted if someone could explain it to me in the style.

In: 1

Th earth is (roughly) a sphere, sorry flat earthers.

Unfortunately that means it’s mathematically impossible to accurately depict it’s surface on a square map (imagine the reverse, trying to wrap a square piece of paper around a ball, without any gaps, creases or cuts, and it should be easier to understand why)

This means we need to use projections to display maps of the earth, these projections will either distort the size, shape or both of the surface, to allow them to fit on a square map.

You can imagine the Mercator projection as having the earth in a tube, and then you slowly inflate it, and each area of the earths surface is mapped as it squishes against the side of the tube.

Because the top and bottom of the earth need to be inflated much more until they touch the tube, the size of anything north or south of the equator is stretched, the further north or south it is the more it’s stretched.

This has the naughty effect of making Greenland look about the same size as all of Africa, when in real life it’s about the size of Greenland.

[Map Men has a good video on the Mercator projection](

basically, take a classic globe with a light in the middle. around it, you place a piece of paper in a cylinder. Now draw the shadow of the world map you see projected on the paper onto that paper.


Congratulations! , you have a Mercator projection. that is literally what Mercator himself did when creating it.


the “stretch” is because your trying to represent a 3 dimensional object (the surface of a globe) in 2 dimensions. the process will, invariably, cause some distortions, so it becomes a question of what you want to preserve. Mercator projections stretch the size of landmasses close to the poles, as your projecting at an angle (think a film projector aiming upwards, the top of the projection is “wider” than the bottom, due to perspective)

Mercator projections have been historically favoured because they preserve the relative angles of latitude and longitude. What that means is, if you plot a course on the map of, say, 80 degrees east, you don’t need to make any alterations to that for actual travel, you can sail on a heading of 80 degrees and arrive at your destination.

A lot of other map projections lose this element in the process of preserving something else (like relative size of landmasses)