A news story last week was the the UN approved a resolution to encourage the use of the Equal Earth map projection and to discourage the use of the Mercator projection. There were a number of things about this story and the commentary about it that annoyed me. The topic also raises several other questions and thoughts.
There are countless different map projections – ways to make a flat map of our round earth. If you look at a small part of the earth, it’s basically flat, but to make a map of the whole world, some parts will be stretched, things will end up as different sizes and shapes, depending which projection you use. The only world map without distortions is a globe.
The Mercator projection is the most commonly used one, for reasons I’ll explain soon. (I’m including Web Mercator here – it’s basically the same as original Mercator). It has the problem of making places further from the equator appear larger. Compared to the equator, places at 30° are 1⅓x the area, at 45° they are 2x, at 60° 4x, at 75° 14.9x, so Greenland (60-83°N) appears about the same size as Africa (37°N-35°S) despite Africa being 14x Greenland’s area.
This issue is sometimes described with a global justice angle: Most rich countries are well north of the equator, so have their sizes inflated, while most poor countries are nearer the equator. People regularly seeing a map with Europe/Russia and North America inflated relative to Africa and South America may think of the former continents as more significant than they might if they saw their actual relative sizes. This was taken up in The West Wing in 2001, where people lobby the US government to change to using equal-area world maps in education for this reason. Fans of the show are amused that something like it has happened in real life with the UN 25 years later.
Now for my gripes. Firstly, some of the commentary has implied that much of the world has only been using Mercator maps. This is not true; books with world maps usually use a more suitable one. From my vague memory the maps displayed at school were of various projections. “Finally seeing Africa’s true size”, as if there hadn’t been equal area projections on classroom walls for decades.
Secondly, the big one – a misrepresentation that often goes unchallenged, even in the UN resolution itself. As an ABC article said “… the traditional Mercator projection, which was designed for maritime navigation by Flemish cartographer Gerardus Mercator in 1569”. They make it sound like it was developed according to the needs of the seafaring Europeans long ago and became entrenched like the Qwerty keyboard, despite there being nothing special about it.
While navigation was a key issue in the 16th-18th centuries, that misses the point of what the projection is and why it’s used more than any other. Zoom in on any point of a Mercator map and you have a non-distorted north-up local map. Other projections don’t do that. The Mercator projection is a bad map of the whole world that contains very good local maps of every small non-polar part of the world. That’s why it’s used so often. That large map on the classroom wall does poorly at illustrating the whole world, but every small country is shown with its correct shape. And in the 21st century, web mapping systems like Google Maps use (Web) Mercator so you can zoom seamlessly. That poorly proportioned world map is the contents page of an atlas and street directory.
Thirdly, the issue was presented by some as a binary – this map versus that map, ignoring the existence of the many other projections in common use that are some kind of compromise between preserving area and preserving shapes (or other equal-area projections).
Fourthly, there were so many posts around the internet that purported to show one or both projections and got things wrong in so many ways. In some cases content creators using AI tools and not bothering to check for mistakes. In some cases deliberate untruths.
Finally, much of the commentary missing the point that people are exposed to Mercator not because it has any special place in education but because of convenient web services like Google Maps (which is primarily for local maps). In the old days the maps people saw were typically produced by people who knew what they were doing (and usually used an appropriate projection for world maps). But now it’s easier to make a map and people will use whatever is easiest.
Now for some questions that this story got me pondering.
The various compromise projections still make Greenland look large, just not ridiculously so. Does a fair view of the world need to go all the way to equal area, or is one of the compromises adequate?
Would the Mercator projection have been used as much in earlier years if it made Europe look smaller?
During the Cold War, did westerners fear the USSR more because they were so big on the map?
If we object to an unequal area map because it makes some countries more prominent than their real area warrants, are we assuming that countries should be prominent if they’re large in area? Maybe cartographic equality calls for more area cartograms.
Finally, a reminder to use the best tool for the job. I’m not an expert so you’ll find much better advice elsewhere, but here’s my mine. For local maps, Mercator works fine and no one will be thinking about projections. For a large country, you want one that’s as though you’re looking directly at that part of the globe. I’ve used Albers for maps of Australia.
When it comes to the whole world (or a majority of it), that’s where there will be tradeoffs. You’ll have distortion of one sort or another. If it’s a map of land use or average temperature, area is worth preserving – go with an equal area projection. If it’s a map of airline routes, you want to preserve distances as much as possible. The projection you choose depends on what you’re happy to go without. Do you need north up (or sort-of-up)? Do you need Antarctica? Could you sacrifice continuity in the ocean to reduce distortion in continents? Which part of the world will you cut through? Which are OK to get stretched?
And if you are going to use Google Maps because, being a normal person, you’re unfamiliar with GIS tools that nerds like me use, then at least chop off the Arctic like you do the Antarctic.
A final thought. It’s one thing to discourage the use of Mercator; it’s another thing to advocate for equal area; but the UN resolution went a step further and advocated for the Equal Earth projection. That seemed a step too far, especially if you’re thinking about web mapping systems, which is where the most people are seeing the continents out of proportion. I can see a rectangular equal-area projection (eg Gall-Peters) working in a web map, not smoothly like Mercator, but well enough. With Equal Earth, not a chance.