Map Monday: what are map projections and why do we need more than one?

The map in last week’s Map Monday showing how many countries and continents could fit into the same size as Africa surprised many readers. These are the same readers who know a lot about geography. Just goes to show how our minds have been warped by spending our entire lives looking at world maps with a Mercator projection. For those of you who aren’t sure what that means, it’s this common map of the world in 2D (i.e., as opposed to a 3D globe) we’re all most familiar with:

Image credit: worldmaps.com (Click on it to enlarge)

The Mercator projection is formed by taking our 3D world, a sphere, “unattaching” it from the North and South Poles, and rethinking the world as a cylinder. It stretches the top and bottom parts of the world so that all the lines of longitude (the lines that meet at the poles and go from pole to pole, like the Prime Meridian at 0 degrees, which runs through Greenwich, England) are straight vertical lines on a 2D page and all the lines of latitude (the lines that run parallel around the globe, including the Equator, the Tropic of Cancer, the Tropic of Capricorn, the Arctic Circle, and the Antarctic Circle) are straight horizontal lines. For starters as to the downside of this approach, the Equator at the middle of the globe is far bigger than the Arctic Circle, yet on the map we usually look at they are the same size. The relative positions of countries and oceans are reliable, but not their relative sizes. The further away from the Equator you get, the more inaccurate the relative size.

Mercator projection in light blue, actual sizes of the countries in dark blue. Image credit: visualcapitalist.com

So why do we use such a map if it’s so misleading? Because it’s pretty darn useful. It was developed way back in 1569 by Belgium cartographer Gerardus Mercator. It’s actually brilliant if you’re a navigator, because it is the easiest possible way to identify the longitude and latitude of every bit of the territory on the globe, all on a handy-dandy 2D piece of paper. Far easier than trying to figure it out on a globe as you’re sailing around the world. Or doing nearly anything that requires navigation, especially in the 430 or so years prior to GPS!

So what other options might we have to get a handle on how big various parts of the world really are? What are some alternatives to the extremely enduring Mercator projection? They’re all creative; none are as good for navigation as our 450-year old Mercator!

Two views of Buckminster Fuller’s dymaxion map, showing how he’s taken recast the globe from a sphere to an icosahedron (20 sides) and then opened it up to flatten it, preserving the relative distances. Image credits: newatlas.com

The Visual Capitalist has some fun tools for superimposing different countries and continents on top of others to get a better feel for true relative sizes. You might want to give it a try yourself.

Australia and Indonesia superimposed on Canada and the U.S. Image credit: visualcapitalist.com

Another visualization of the actual size of Greenland moved down to be near Brazil. Image credit: visualcapitalist.com

Canada looks far bigger than the U.S. in standard maps, but in fact it’s only slightly bigger. Image credit: visualcapitalist.com

Enjoy!