It can get pretty quiet here. See Bostonography or Axis Maps for some other posts.

A blizzard of purple

The blizzard of doom was impending. The French Toast Alert siren was blaring. But I wasn’t home in Boston to witness the fun. So, what else to do but look at all the snowfall prediction maps?

Meteorology is a bastion of the rainbow color scheme. The bigger the storm, the more maps. And the more maps, the more colors! It gets especially fun when sequential maps need to extend beyond their usual range. (Remember when Australia was so hot that they had to add a new color?) Perhaps that was a factor in this storm, since the amount of snow was predicted to be unusually high for the affected area.

That said, most maps I found weren’t too out of the ordinary. Here are a few examples.

This one on had a classic looping color scheme. “Okay, we’ve got blue, then purple, then pink, then… crap, what comes after pink? Probably a different kind of blue.”

Snow map from

The National Weather Service put out maps like this one, with a gray-blue-purple scheme.

National Weather Service snow map

But there were also maps like this, grabbed from the Facebook page of the NWS office in Taunton, Mass. (Go ahead with the tauntaun jokes, nerds), where purple was not enough and red—the most dangerous color of all—was necessary.

National Weather Service snow map

Springer Cartographics put this up on Mapbox. When an expert cartographer makes such a map, you get what appears to be a ColorBrewer scheme.

Snow map from Springer Cartographics

The Boston Globe was at first slinging NWS maps, but later replaced it with this, which appeared to come from the AP. Pretty simple, with wide class ranges.

Snow map on the Boston Globe

The New York Times also first had a map from the National Weather Service. This one threw green into the mix.

NWS snow map on the New York Times

Later in the day, that map had been replaced by a much more NYT-ish map. This is a nice example of something Tim has explained in the past: when timeliness is paramount, put up something acceptable (in this case the NWS map), then later revisit it with refined design.

Snow map on the New York Times

Finally, we musn’t forget the Weather Channel. This map is disappointingly not panic-inducing, considering the source. Imagine it within an overblown page containing annoying auto-playing video, though. And at least it’s oblique.

Weather Channel snow map

Happy sledding, everyone!

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On practical cartography

Another carto-year has come to a close. A carto-year is measured from October to October, or more specifically, between NACIS conferences. If you’re not a NACIS regular, come to a few meetings and you’ll understand. It’s the New Year’s Eve of cartography—an intellectual, visual, and social celebration of mapping that at once exhausts you and leaves you excited for things to come.

Maptober road trip. “Map selfie” by Mike Foster.

It seems that the theme of my carto-year was practical cartography: those everyday details of working with data, using software, writing code, and so on. The how of cartography.

For a second year I co-organized Practical Cartography Day at NACIS (this time with Rosemary Wardley of National Geographic), a pre-conference day of presentations focused on tips and tricks of everyday mapping, as opposed to less hands-on topics like theory, map use, or even design. We had twenty presentations, from bite-sized tips to software demos to behind-the-scenes looks at how some cool maps were made. PCD drew a crowd of 150, about half the size of the main conference. Most of the talks have slides or other material online, so check out the links in the schedule: parts 1, 2, 3, and 4.

NACIS group photo by Alethea Steingisser. Scores of smiles, plus Matt Wilson looking at his phone. #notmattwilson

Back home, a few of us jumped on the Maptime train and established a Boston chapter. Jake Wasserman, Mike Foster, and I shared the goals and frustrations that gave rise to the original Maptime: there’s a ton happening in mapping right now, and it’s hard for newcomers to find a friendly and supportive learning environment. We’ve held five Maptime Boston meetups so far, mostly focused on tutorial exercises. It’s been so nice to see people learn something new, then come back and share a map they’ve made with those new skills. Meanwhile, veteran mappers also show up and happily share their know-how. See some Maptime Boston stuff on GitHub, and if you’re anywhere near here, be sure to join the Meetup group.

Maptime Boston, or for Ryan and me, Snacktime Boston.

Another event was a short “mapshop” at the University of Kentucky immediately following NACIS, hosted by Matt Wilson and Rich Donohue. This involved Rich and four of us guests (John Czaplewski, Mike Foster, Carolyn Fish, and I) sharing perspectives on different aspects of “new maps,” which mostly meant showing some demos of various tasks and tools. That’s in spite of a critical bent at UK Geography—I was described as the “capitalist” among the guests, which I guess means the only one who has a normal job outside a state university.

Rich, me, Carolyn, Matt, John, and Mike, temporarily not on a bourbon distillery tour.

That’s all to say that I’ve been increasingly interested in “how?” as the primary question of cartography, at least in a learning process. This may be in contrast to some things I’ve rambled about in the past. I still believe in thoughtful mapmaking and asking questions beyond the technical, but most of those questions are secondary—not in the sense of being less important, but simply in the sense of coming later. Learn to make a map before learning to make a good map. If you don’t start with the how, you’re going to struggle.

The state of cartography is strong thanks mostly to those who ask “how?” before anything else. It’s interesting to revisit a Denis Wood rant against academic cartography from 2003, Cartography is Dead (Thank God!), taking it to mean that cartography—sorry, mapmaking—has always been about the doing. If Wood was to be believed a decade ago, it’s all even more true today, as web mapping grows explosively under the leadership of technical people who may scarcely be aware that any other level of cartography even exists.

Cartographic technology.

On the other side, academic cartography still appears reluctant to embrace modern technical skill in education, saying something like “cartography isn’t about the tools” even though modern tools have thoroughly transformed the practice. I always attend cartographic education panels at conferences (NACIS and FOSS4G this year) and listen to educators discuss—to no avail, generally—their struggles with teaching concepts and not just button-pushing… or code. From the sound of it, the usual result is an awkward lecture/lab split in which students receive barely enough technical instruction to make a map, never mind actually realizing most of the concepts they learn in lecture.

I’m not close enough to academia these days to say much more about it. Suffice it to say that how is the hardest part of mapping, and is a vital part of cartographic education. It’s not enough to know what a good map is; it’s necessary to know how to make it. A failure to grasp lecture material might keep one from being a stellar cartographer, but a failure to grasp lab material will keep one from being a cartographer at all. Don’t push aside technical skill for fear of neglecting theory and design concepts. Participation, not pedantry, is the means for formally educated cartographers to affect the current technology-driven cartographic progress. Make room in a curriculum to teach the technology right. When it’s done well, technical skills are extensible, not just an exercise in button-pushing.

Continue to ask “how?”. Learn the technical skills, or teach them if you are an educator. Don’t seek perfection in design until you actually know how to build it. But don’t ever be intimidated; remember that learning how to make even the simplest map, just a pushpin on your house, is an amazing accomplishment. From there, you can go anywhere.

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“It’s just a population map!”

Thou shalt not take xkcd 1138 in vain.

It’s nice that xkcd provides the occasional popular exposure of cartographic topics, but unfortunate that it makes critics’ jobs easier. The comic linked above has been invoked often since it first appeared, including in response to everyone’s latest favorite map to hate, US GDP Split in Half.

GDP map

If you’re a map person you’ve already seen this a thousand times, often accompanied by hyperbolic words like “incredible,” and you’ve also seen a thousand complaints about how it’s meaningless and simply a map of population density. (Indeed, I was not about to let an opportunity for snark slip by, despite my stated support for bad maps.) The argument is that most people in the US live in metropolitan areas, so of course that’s where most of the economic activity will come from.

Is that true? There are reasons why the map doesn’t say anything significant about economic activity—one of them being that it’s totally arbitrary and there are infinite ways to divide GDP in half geographically—but “just a population map” is a cheap and thoughtless dismissal. The only thing that is actually a population map is a population map.

In this case, the numbers show that it’s not quite a population map. The 23 metropolitan areas account for half the GDP but only 39% of the population, and, by extension, their per capita gross metropolitan product is 50% higher than the remainder of the country. There’s wide variation among the metro areas, too: San Jose’s per capita GMP is nearly twice that of Phoenix. Here’s a version of the map with a little extra information based on 2012 source data and population estimates (corrected to show metropolitan areas, not urbanized areas).

GDP and population

That’s not to say the original map did a good job of highlighting contrasts between population and economic activity, or really anything at all—it doesn’t expose any population information, and the arbitrary grouping means that these 23 metros are not necessarily more special than any others—but the point only is that the contrasts do exist and the map is not simply a population map.

So, friends, let’s not be hasty to drop xkcd links and the categorical “just a population map” criticism. There’s nuance to every map, even if we have to go looking for it.


Six map links that every cartographer has seen a million times

We have a problem as cartographers. It’s that nobody would ever in a million years have believed that there’s such a thing as cartography anymore. Whenever somebody discovers (with much amazement) that we do exist, either by joining our ranks or simply realizing that we weren’t lying about our jobs after all, they react predictably. They send around the thing that led to this discovery, or the thing that they found soon after the discovery. And most of the time it’s one of the same few things. Heck, we tweet and retweet these things over and over ourselves, probably because we’re still trying to convince everyone that we exist. Friends, let me save you some trouble. Here are some things that every cartographer has seen a million times; you don’t need to send us these links.

We feel smug every time someone tweets or emails this to us, because we already knew the distortions of the Mercator projection and the social arguments for the Gall-Peters projection. It’s all we can do not to lecture you about it beyond the four minutes of the clip. Don’t get us wrong: we’re kind of giddy that the ever-highbrow West Wing introduced you to the subject, but we’ve seen it a million times.

Nothing is where you think it is.

Okay, this one isn’t a link people send us. But, every time. Every time we mention our job to someone new, this is what we hear in reply. Or something along those lines, anyway. We’ve heard it a million times and we’re tired of answering it.

You make maps? That’s so sad!
The inevitable conversation

Buster thinks that blue on the map indicates land, LOLOLOLOL!!!111!!1!one. Okay, we can laugh at Buster for that one, but the harder joke to swallow is the one earlier in the episode, which kind of dismisses cartography because everything has been discovered by Magellan, Cortés, and NASA. Oh well. Cartographers are cool, so we’re Arrested Development fans, which means we’d seen this a million times before you ever sent it to us.

Never hurts to double check.

Every few months some notable outlet runs a story on the growing interest in things like OpenStreetMap and the ever-increasing accessibility of mapping tools and data. Admittedly these aren’t written for us—and they provide excellent exposure for good things—but they still fly around cartography circles. Hey, we are keenly aware that amateur cartographers are everywhere. Why do you think we get so cranky and act like know-it-alls? Because a million amateurs are going to STEAL OUR JOBS!

What’s next, robots?
Uncharted Territory: The Power of Amateur Cartographers
What Happens When Everyone Makes Maps?

These appear almost monthly now and come in a few flavors, ranging from Buzzfeed nonsense to respectable journalism. They tend to follow a pattern, which is to include:

  • A half dozen superbly crafted, informative maps
  • A handful of disgusting cartograms
  • About 20 maps that simplify complex world issues into bite-sized MS Paint-quality choropleths

Trust me, the only satisfaction we get from these is seeing that some of our colleagues made the list. (Those would be the several good maps.) Otherwise we cringe. Also, we’ve already seen all the maps a million times. We’ve seen this 26 million times before.

Look at the title of this post! Ha ha ha!!!
40 maps that explain the world
40 maps they didn’t teach you in school
38 maps you never knew you needed

Harry Beck must be rolling over in his grave. The subway map infographic craze was in full swing a couple of years ago, with people “visualizing” all kinds of things using this well-known style. Yeah, it’s a nice visual, but folks: if there isn’t actual topology to show, it shouldn’t be a subway-style map. Among the popular images that get passed around are some magnificent maps that actually make sense (often dealing with transportation, for example Cameron Booth’s maps), and a few of the others are clever enough to be worthwhile, but we cartographers do a lot of eye-rolling at the rest of them. A million eye rolls.

But this is one of the clever ones.
xkcd subway map

I am in reality only half as rude as the above post may suggest.

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Why are choropleth Mercator maps bad? Because we said so.

The other day I was speaking to a non-map person about the problems with choropleth mapping on the Mercator projection and went looking for a link to something that could explain it more clearly than my bumbling self. It became a familiar exercise, because I’ve done this before: there’s hardly anything out there on the web that really explains this problem in clear detail. We talk about Mercator choropleth maps often enough, and the idea of them ranges from ill-advised to anathema, but we hardly go beyond simply saying “it’s bad because areas are distorted.”

So, two things. First, we could stand to share knowledge better, cartographers! Everyone is pretty good at sharing code and data these days, but we fall short on sharing the why of things, especially those of us who went to school for this and everything.

Second, an attempt at uncovering the problems with choropleth mapping on the Mercator projection.

Now, perhaps nobody really talks about why small-scale Mercator choropleths are bad because the gist of the reason is intuitive enough: bigger looks like “more,” so any map projection that distorts area (especially as severely as Mercator does) will make some values look exaggerated and will thus be misinterpreted. Size comparison is at the heart of many types of statistical graphics, and obviously relative sizes need to be correct for the whole concept to make any sense at all.

Distortion on the Mercator projection

Indeed, this sometimes applies to areal mapping, for example “land-use or similar mapping in which a measure of the area occupied by some distribution is crucial to map interpretation” (Muehrcke and Muehrcke, Map Use 3rd ed.). If you need to compare areas, areas cannot be distorted. (Never mind that humans are terrible at estimating and comparing areas of irregular shapes, from what I hear.)

In the typical choropleth map, however, area is not directly the visual variable of interest, and we are not trying to measure it. Still we assume that relative sizes need to be true in order for the map to work. How do we know that? Well, I’m not sure. I flipped through all my cartography textbooks and to my surprise it’s not that I forgot the evidence for this—it’s that they really don’t cite anything on the subject. We accept it on faith and common sense, apparently, although I’d bet a shiny nickel that someone somewhere has done empirical studies to confirm it, or that somewhere buried in How Maps Work is an explanation. Please, if anybody can point me to some of the research behind all this, it would be appreciated!

Choropleth and proportional symbol maps

It turns out, then, that this is not just an internet problem. A textbook education in cartography will not teach you, in scientific terms, why a choropleth Mercator map is worse than a choropleth sinusoidal map or a proportional symbol map. Interpretation of area in quantitative maps gets no quantitative explanation; instead it gets basically the same treatment as propaganda maps and the whole Peters thing, which paraphrased boils down to “bigger things totally look more prominent and important because they’re bigger.” Semiology of Graphics is the only book I have that really addresses size directly and as matter of fact—noting among other things that “it is not possible to disregard it visually” and “in any map representing areas of unequal size, what is seen is [quantity] multiplied by the size of the area”—but even if he was correct, Bertin was pretty much making things up.

Mentioned more commonly but no more deeply explained is the need to normalize data to account for area in choropleth maps, i.e., not mapping counts. Considering this rule, the projection requirement, and a host of “ideal” enumeration unit characteristics, choropleth mapping just starts to sound like a terrible idea for anything at all. Size variation that is not directly related to numerical variation seems to cause nothing but problems. Danny Dorling’s arguments for cartograms and mapping human phenomena in human space, not geographic space, start to sound appealing.

Too bad cartograms are also kind of awful.

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Free as in painstaking cartography labor

There are ways in which I think cartography is an under-appreciated and poorly understood field, some of which are enumerated in occasional rants on the Axis Maps blog and elsewhere. But these are usually philosophical or academic matters, and as someone who is making a career of cartography, increasingly I’ve been trying to offer this piece of advice (which isn’t as obvious as it should be) to aspiring map people: cartography skills are valuable, as in dollar bills.

Hence my—and some peers’—disappointment in the most recent “challenge” from the MBTA, Greater Boston’s transit agency. To summarize a somewhat lengthy description page, they are essentially seeking new design ideas for their standard subway map—in the space of three weeks, for free, and with no rights retained by the cartographer. And if you win this contest? You get… um, fleeting glory, apparently.

MBTA map

I want to like the idea. The MBTA carries crippling debt, and as a somewhat regular user of the system I don’t want to see its service diminished or my fares increased, so I applaud any other funding or savings. But—and I’m looking for some kind of “third rail” wordplay here—this time they strike a nerve with those of us who have mapping jobs.

The T has run contests before. The most successful was a few years ago at the dawn of its open data age, resulting in some cool visualizations and interesting apps using schedule data, which shortly thereafter was supplanted by real-time tracking. These previous contests, though, were very much about openness. Yes, the clever angle was to get the community to create products at no cost to the agency, but at least these products were not owned by the agency. And there totally were prizes.

From the outside it’s easy to mistake modern cartography for a free endeavor driven by some desire to improve the world. Indeed, we do have a few altruistic motives, and the latest trends are all about openness: open data, open source code, etc. But even these things are not always free. Free to use, yes, but often enough someone has paid for them to be made in the first place. And this model doesn’t really apply to design. Good design is a part of any project, open or not, but when the job itself is design, we don’t jump at the chance to do it for someone else without compensation just because it’s fun. Like everyone else in the world, we do this to earn a living.

In short, if you can design a subway map that’s good enough for millions of people to use on a daily basis, you are very good at this. Maps are easy. Good maps are not. Your skills are valuable. Make maps for fun when it’s for your own satisfaction or for the causes you champion, but recognize your worth when it’s for others’ satisfaction. And make them recognize your worth, too.

In any case, while we’re on the subject, do enjoy Cameron Booth’s MBTA map redesign—which the MBTA can’t have for free—and Peter Dunn’s time-based map.