Why you should be upset Boston Public Schools has adopted a new map

Alex Tolkin
Mar 22, 2017 · 5 min read

A bunch of articles have been circulating the internet praising the Boston Public School (BPS) system’s decision to adopt a new map. They are replacing the old Mercator maps with maps using the Gall-Peters projection. The Gall-Peters ensures that landmasses are all the correct size. The traditional Mercator projection dramatically distorts size, for example dramatically inflating the size of Europe and decreasing the size of Africa. So this is great right? This is a blow against entrenched imperialism in the classroom?

No. It’s a bullshit combination of academic politics, ignorance, and misleading advertising. Fuck Gall-Peters. Let’s talk about map projections.

Because the earth is round, it’s impossible to have a perfect map, because you are trying to translate a sphere onto a flat shape. Every map has trade-offs. The Gall-Peters map is bad because it has numerous disadvantages and no unique advantages. But before we get to Gall-Peters, let’s talk about the most famous map projection; the one being replaced at BPS; the Mercator.

The Mercator, a classic map you are probably familiar with

The Mercator projection was developed in 1569 by the German Gerardus Mercator. It caught on as a phenomenal map for navigation because it has straight loxodromes. A loxodrome is a line that crosses every meridian at the same angle. This is useful for maritime navigation because if you follow a loxodrome you never need to change your bearing. In other words, if you set a course 34 degrees south-southwest, on the Mercator projection you will follow a completely straight line. For 16th century navigation that was an invaluable asset. Additionally, at short distances linear scale is preserved in all directions, which is why every online map service I know of still uses the Mercator. At long distances, distortions systematically pile up to dramatically shrink shapes near the equator and enlarge them near the poles.

Notice how the loxodrome (rhumb line) crosses every meridian at the same angle. It’s a longer route but easier to navigate. The Mercator was designed around simplifying loxodrome calculations.

Once having a really good maps became interesting to people other than explorers and sailors, the Mercator’s problems became more serious. Cartographers realized that the Mercator is great for navigating a ship, but not that super as a general purpose map because the sizes are all wrong. So cartographers through the 19th and early 20th century used all sorts of mathematical properties to construct all sorts of alternative projections. One projection was developed by clergyman James Gall in 1855. This made sure areas were correct by distorting shapes at the poles and the equator — stretching at the equator and compressing at the poles. It never really caught on, because while the sizes were correct, more or less everything else was wrong. Besides, equal-area maps had been around since before Mercator, so this wasn’t really anything new.

In the first half of the twentieth century, cartographers made a push to replace the Mercator as an educational tool. The most notable push came from Trystan Edwards, an amateur cartographer with an equal area projection map of his own. The New York Times even wrote an editorial advocating ditching the Mercator back in 1943. None of this had any effect on the public.

The Eckert IV projection from 1906. This has correct areas and close to correct shapes

In 1973, German historian Arno Peters presented his brand new “Peters Projection”. Peters claimed that the Mercator was prominent due to European imperialism. Its size distortion was a reflection of how Europeans ignored Africa and inflated their own importance. Furthermore, his map was the only map which showed areas correctly, as well as being “totally distance factual” with “no extreme distortions of form”.

The Gall-Peters projection. Areas are correct, everything else is wrong.

Cartographers responded with a collective “what the fuck?” to this pronouncement as it was literally entirely wrong:

  • The Mercator was popular due to navigational advantages, not to inflate European ego
  • There are loads of maps that show equal area
  • The Peters projection isn’t distance factual
  • The Peters projection heavily distorts forms
  • This wasn’t even a new projection! It was identical to the old and ignored Gall projection of 1855!

But Peters was better than cartographers at two things: academic politics and lying. He refused to acknowledge Gall’s map at all (at least until years later when the controversy faded from popular press). He claimed cartographers were agents of imperialism, blinded by their perceived dominance over “primitive peoples”. He further claimed that due to their biases, cartographers were incapable of developing a fair world map, discrediting the entire profession, despite the fact that cartographers had brought up Peters’ own complaints in the past and done a better job at resolving them.

This response was, like Peters’ original announcement, nothing but lies. But Peters was effective at selling a narrative of cartographic imperialism to other historians who didn’t know or care about loxodromes or angular distortions or any of the math behind cartography. They saw the map controversy through the narrative they were familiar with and wanted to believe — an upstart ripping down the prejudice of an antiquated and biased profession.

Perhaps the silliest part is that the Gall-Peters isn’t even good at fighting against the imperialism it supposedly combats. Shapes near the equator and poles are totally distorted, so the only part of the map that actually looks correct is (you guessed it) Europe. Other map projections, such as the one proposed by Edwards decades before Peters, make sure that equatorial areas look correct (at the expense of Europe and the US).

The Hobo-Dyer map has correct size and most things are close to the correct shape, except Europe

Back to the Boston Public Schools announcement. The only distributor of Peters projection maps in North America is ODT maps, so they essentially have a monopoly on the shitty Peters map. Guess where ODT is headquartered? Massachusetts of course, which might explain how they got this sweet deal to sell an inferior product to the public schools. And their maps come with little sidebars that explain how great the Peters projection is. ODT also does “advocacy” work fighting to promote the Peters projection (sell the product they have a monopoly on) instead of the numerous other, far superior maps. And they’ve been successful enough that the Peters projection now seems to be the default non-Mercator in popular culture.

The “Natural Earth” projection, a relatively modern projection that is a compromise map. It doesn’t do anything perfectly, but it does a lot of stuff well, making it a solid choice for a general-purpose map.

I’ll end with a great xkcd comic on projections that says it all -

Alex Tolkin

Written by

Communications/Political Science PhD at University of Pennsylvania

Welcome to a place where words matter. On Medium, smart voices and original ideas take center stage - with no ads in sight. Watch
Follow all the topics you care about, and we’ll deliver the best stories for you to your homepage and inbox. Explore
Get unlimited access to the best stories on Medium — and support writers while you’re at it. Just $5/month. Upgrade