I’ve been struggling for months now on how to deal with Arno Peters and his world map. Every time I turn to the subject, I just get bogged down by the complexity of the scattered and multifaceted literature, by the insanity of much of Peters’ map work, and by the different responses to his work. […] After at least three tries to say something new, and floundering each time, I am presenting this blog entry simply as an attempt to organize the information about Peters in a way that makes sense to me, which is to say historically. Think of it as a long bibliographical essay based on what I have to hand (so not comprehensive, especially in the German-language literature). I’m not sure that it says anything necessarily new or significant. So please join me as I go through a series of cuts at Peters and his map work.

The Gall-Peters projection is a second-rate projection with first-rate public relations; cartographers’ responses to the projection that focused on its cartographic shortcomings ended up missing the point. Something different is happening with the Equal Earth projection, which was announced last month as a response to Gall-Peters: an equal-area projection with “eye appeal.” It’s getting media traction: the latest news outlet to take notice is Newsweek. So, finally, there’s an alternative that can be competitive on the PR front, without having to mumble something about all projections being compromises until the eyes glaze over.

It’s turning up in GIS packages, too: in D3, in G.Projector and in proj4. There’s even a t-shirt.

Previously: The Equal Earth Projection; Equal Earth Updates.

Previously: More on Boston Schools and the Peters Map; The Peters Map Is Fighting the Last War; The Peters Projection Comes to Boston’s Public Schools; In Defence of the Mercator Projection; How the Mercator Projection Won the Internet.

Joshua Stevens, NASA’s data visualization and cartography lead:

(2/2) Are kids being taught that? If so, adopting any *1* projection is counter to learning why *many map projections exist & have purpose*

— Joshua Stevens (@jscarto) March 23, 2017

Also on Twitter, and to emphasize how long this has been going on, Jeremy Crampton notes his 1994 paper, “Cartography’s Defining Moment: The Peters Projection Controversy, 1974–1990.” A sequel may be required.

Previously: The Peters Map Is Fighting the Last War; The Peters Projection Comes to Boston’s Public Schools; In Defence of the Mercator Projection; How the Mercator Projection Won the Internet.

The Gall-Peters projection is just one of several rectilinear equal-area projections; that Peters promoted it as a tool of social justice and anti-colonialism made it awfully appealing to people who are concerned with such issues. (They are not wrong to be concerned with such issues.) But cartographers have generally always been appalled by the projection, by Peters’s rhetoric and by his general ignorance of what had gone before. (Peters’s map had already been described by James Gall in 1885; the Mercator projection‘s insufficiencies as a wall map had long been known; and there were many other projections, from the Van der Grinten to the Mollweide to the Goode homolosine, that were already being used in the Mercator’s stead.)

(The Mercator projection, for its part, makes a crap wall map: its virtue is that rhumb lines—compass headings—are straight lines, making the Mercator ideal for navigation. It’s worth emphasizing that Mercator himself died in 1594. Again, see Monmonier’s book on the subject.)

Cartographers’ response to the Peters projection is essentially, usually (and correctly) that every map projection is a compromise, because every map projection is an attempt to represent a round planet on a flat surface. All maps, in other words, lie; or at least no map is exempt from lying; or at least the Mercator is no more a liar than any other projection. It’s essentially an effort in debunking—the tedious repetition of “well, actually” to a credulous audience that doesn’t care enough to listen all the way through. (And besides: the company selling the Peters map thoroughly agrees with them!)

For the latest examples of this, see Caitlin Dempsey’s piece on teaching context, and Andy Woodruff’s response to the latest round of this. They’re good pieces, worth reading—but I can’t help wonder whether something different needs to be tried. But then again: what problem are we trying to solve? Media and public credulity? The fact that the Peters projection, bluntly, sucks? The campaign—and it is a campaign—behind it?

But the campaign for the Peters map is increasingly irrelevant. In late 2015 I argued that the debate over the right projection for wall maps was the cartographic equivalent of fighting the last war. The Peters map was a 20th-century response to a 19th-century problem (the Mercator on wall maps) that had already largely been solved earlier in the century. Sure, there are still wall maps out there that use the projection (I’m looking in your direction, IKEA), but by and large it’s not used nearly as much as the Peters defenders would have you think.

But 21st-century mapmaking is not about wall maps: it’s about web maps. As I said in 2015:

Every online map service uses a variant of the Mercator projection called Web Mercator. Whatever its shortcomings—and there are many, owing to the fact that its calculations use a spherical Mercator model to save computational cycles—Web Mercator has become the de facto standard. And the size distortions at small scales that have made the Mercator projection the target of so much ire over the decades are simply moot for most use cases.

In many ways the past debates over the Mercator are moot: arguing over the right projection for wall-sized world maps—Mercator vs. Peters vs. Robinson—is fighting the last war. Mercator has become the default option for online mapmaking, simply because so many data visualization maps rely on Google Maps or OpenStreetMap for their base map layer. Other projections will be reserved for the professionals, people with access to more sophisticated mapmaking tools and the skill to use them, but for the most part, when data is mapped on the Internet, it’ll be mapped according to Mercator.

Zoom out in Google Maps or OpenStreetMap, and what do you see? The Mercator projection, with Greenland in all its inappropriately giant glory. (Apple Maps turns into a globe when you zoom out far enough, but Apple Maps are app-only.) The reason why this isn’t generally seen as a problem is that hardly anyone uses Google Maps as a world map: like topographic maps that use UTM, at close range Mercator works just fine.

While there are efforts under way to use other projections in web maps, it’s unlikely that the Mercator-vs.-Peters battle—a false dichotomy if there ever was one—will migrate to the digital arena.

Previously: The Peters Projection Comes to Boston’s Public Schools; In Defence of the Mercator Projection; How the Mercator Projection Won the Internet.

In a development that just might make academic cartographers pull out their remaining hair in frustration, Boston’s public schools began using the Peters projection in social studies classes last week. The news coverage (see the Grauniad’s) is the usual straw man argument about the Mercator and the false dichotomy between it and the Peters, as though no other map projections have ever been used. (National Geographic has been using other projections since the 1920s, and currently uses the Winkel tripel. The last time I was at a map store, hardly any of the world maps for sale used the Mercator. See Mark Monmonier’s Rhumb Lines and Map Wars: A Social History of the Mercator Projection, which I reviewed in 2008.)

I’ve said it before: if you want to start a fight among cartographers, ask them what their favourite map projection is. Earlier this week I did just that: I felt mischievous and wanted to try out Twitter’s polling feature, so I ran a poll asking my Map Room followers what the best projection for world maps was. And because I was feeling particularly mischievous, I made sure to include both the often-reviled Mercator projection and its antithesis, the Peters projection, rounding out the list with two less controversial choices: the Winkel tripel projection used by National Geographic, and the brand-new Patterson projection announced late last year.

The results of the poll were utterly unexpected: 42 percent chose the Mercator projection.

Cartography fight! The best projection for world maps is:

— The Map Room (@maproomblog) November 25, 2015

I was trolling the Internet, pure and simple, and in the end I got trolled back. Fair enough.

Then again, maybe I wasn’t. The more I thought about it, the more I realized that, whether they knew it or not, the voters had a point. Because when you think about it, the Mercator projection has won in the cartographic arena that really matters today: online mapping.

Every online map service uses a variant of the Mercator projection called Web Mercator. Whatever its shortcomings—and there are many, owing to the fact that its calculations use a spherical Mercator model to save computational cycles—Web Mercator has become the de facto standard. And the size distortions at small scales that have made the Mercator projection the target of so much ire over the decades are simply moot for most use cases.

In many ways the past debates over the Mercator are moot: arguing over the right projection for wall-sized world maps—Mercator vs. Peters vs. Robinson—is fighting the last war. Mercator has become the default option for online mapmaking, simply because so many data visualization maps rely on Google Maps or OpenStreetMap for their base map layer. Other projections will be reserved for the professionals, people with access to more sophisticated mapmaking tools and the skill to use them, but for the most part, when data is mapped on the Internet, it’ll be mapped according to Mercator.

(For more on the controversy surrounding the Mercator projection, read Mark Monmonier’s Rhumb Lines and Map Wars: A Social History of the Mercator Projection. I reviewed the book in 2008.)