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!

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

  1. Roy McCarthy says:

    Well I am truly astonished at the relative size distortions, never having given the matter any thought. I’m wondering what else I take as gospel that I’m unaware of? This has been a fabulous series of posts Jane.

    As to maps generally I’m perhaps more enthused by historical mappings of small areas, villages etc., seeing how they’ve changed, or indeed what hasn’t changed. And discovering perhaps where a 100-year-old photographed scene is in the present day environment.

  2. The Mercator is yes misleading but I’d suggest it’s just plain wrong! After looking at all your world maps I’m now more surprised than ever that we still use this projection as THE standard. Btw did you see my ‘Empire Globe’ posting? Loving your maps btw.

    • Jane Fritz says:

      Lol, well, a projection can’t actually be wrong if it’s created according to consistent rules, but it is certainly misleading as far as relative size is concerned very far away from the equator. But it’s perfectly “square” for finding somewhere according to latitude and longitude. If that matters to you! 😏 Glad you’re enjoying Map Monday. And, yes, I did see your globe post. Very interesting.

  3. I just love all these maps you find, Jane. OMG, I had a geography course back in my freshman year of college (as I recall, I took it in place of a math requirement — makes no sense to me to this day, but I was grateful), and I remember the professor teaching us about Mercator! – Marty

    • Jane Fritz says:

      That’s funny, Marty, that you were able to switch a math requirement for geography. Boy, there would be A LOT of students jealous of that option! I’m glad you’re enjoying the maps I’m finding. It’s a fun way of passing time during lockdown. 😏

  4. Pingback: Map Monday: what are map projections and why do we need more than one? – Musings and Wonderings

  5. Jill davies says:

    You must have been a great teacher, Jane, as you have been able to explain the principles of distortion that occur when taking a sphere, our earth, and flattening it to a Mercator projection. And…I understood it! Thanks

    • Jane Fritz says:

      Aww, thanks, Jill. Glad to know I conveyed what I hoped to, at least to one reader. Maybe I should write some posts on what I really did teach, like programming or systems analysis. Or maybe not! 😏

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