Often, we cartographers think of selecting a projection as a boring task.
And for good reason! Projection lectures were often the ones you immediately tuned out as an undergrad. Nothing like listening to a disinterested professor drone on about compromise versus cylindrical versus, blah, blah, blah, radians, blah… at 8 a.m. on a Monday.
I’m here to tell you that selecting your map projection, extent, and orientation is one of the most invigorating steps in the map design process!
Your decisions regarding map projection, areal (i.e., surface) coverage, and orientation are, in my humble opinion, more important for communicating your information, than the actual data you’re mapping. Seriously!
So let’s talk projections! And let’s set aside any bias or prejudice we have about them from our introductory cartography and GIS classes.
3 Steps to Choosing a Killer Map Projection
Things are always more fun when you break them down into simple steps. So that’s what we do here.
The main takeaways?
- Projections are tools for framing/shaping your communication.
- Projections should present your information in a light that is useful and intriguing to your audience.
1. Determine Map Goals and Intended Audience
The first step in any design process, and something you should return to with every design decision you make:
What the heck am I trying to communicate?!
It may be a story, an argument, an experience, a feeling, really important information about feral cats in your neighborhood…
Regardless, the message must drive every decision, including the selection of your projection, map extent, and orientation.
One Simple Ground Rule
If you’re creating a thematic map, you really should use an equal area projection. Otherwise, you’re misrepresenting the data you’re visualizing. It’s okay to distort land masses. That’s what projections do. But misrepresenting thematic data? Take umbrage!
I realize “most” people use Mercator projections now. You probably think:
What’s the harm if I follow suit? It’s easier — particularly in web mapping.
Well… here’s a little story.
I had friends who used to jump off bridges. Had I copied them and thought, “Hey, they jump off bridges, I guess I can too,” I’d probably be dead. Luckily my mom gave me sage advice:
Just because your friends jump off bridges, doesn’t mean you should.
Moral of the story? Don’t use Mercator projections for your small-scale thematic maps just because hipsters do. You may end up dead.
Who is your audience?
That’s not all you have to think about, though. Beyond purpose, the next obvious question is:
Who are you targeting with your communique?
Yes, anyone can read your map. (Just like anyone can read this blog.)
But No… you don’t want to design a map to the lowest common denominator audience (unless you’re creating a generic reference map). I’m not writing this blog expecting my second-grade daughter to understand it.
So who are you targeting? Seniors? Hipsters? Women? Professionals?
Or more specifically: Ruthenian-Americans between the ages of 37 and 42 who live within 30 miles of Bangor, Maine?
Determine the core audience you’re after, and make sure your design decisions resonate well with that group above all else.
This is my favorite map ever. I found it in the Macalester Library in St. Paul, Minnesota, one day. For some weird reason they let me check it out — I don’t think they were supposed to — and I scanned the wall-size map with a cheap scanner and stitched it together with Photoshop 7. Hopefully I don’t go to jail now… but whatever. It would be worth it to share this incredible specimen with the world!
The map was produced for Time Magazine by R.M. Chapin Jr. People always show his “Europe from Moscow” map, but this one is more impressive in my mind. The projection, orientation, and extent he chose was deliberate and insanely effective.
He put the US and ally flags at the very bottom of the map — getting squashed by China, which is looming large overhead. The Earth literally spins downward in this projection too, making it inevitable that China will consume the entire map. The Himalayas look like a bear trap, ready to devour anything eastern China misses. The USSR is up there too, just in case people might think the CCCP wasn’t that much of a threat.
Compare the above projection choice and how it makes you feel compared to the map below. The second map presents the same basic argument around 45 years later. Which one do you think will initiate a call to action on the part of readers?
The take away? Well-chosen map projections help seal the deal on your visual communication.
2. Forget Every Map You’ve Ever Seen of the Place You’re Mapping
Cartography, like all types of design, becomes somewhat predictable. We fall into patterns or tropes. Nowhere is this more apparent in recent decades than with map projections.
Web Mercator (conformal, shape preserving rectangular projection) is chosen for small-scale web maps.
Standard equivalent (equal area preserving) projections are selected for small scale maps thematic maps.
Universal Transverse Mercator (UTM) is used on most large scale maps. Again, north is almost always at the top (see next section). Map projections have become as dull and unoriginal as the local 11 p.m. television news.
One way to gain the attention of your map readers, and to galvanize increased interest in what is being viewed, is to mess with people’s expectations. Due to map reader expectations about how places should look, providing a unique distortion of a place will naturally grab people’s interest. All projections distort, so it’s always best to think of projection selection as “distortion selection.” How do you want to distort the earth today? :-)
You can easily change projections in any GIS software package. However, sometimes it’s best to create your own projections by modifying the ones that come prepackaged.
In the one-minute video below, I show you how to do this in ArcMap. Here we take a map of Somalia and the Indian Ocean and transform it from a Mercator projection to a modified conic projection based off of one designed for southern Asia. It’s always a good idea to play around with projections to find one that is unique to your needs and highlights your message.
Try projecting your mapped area in unique ways that better emphasize the story or data you’re trying to show.
3. Frame Your Area of Interest Like a Filmmaker or Photographer
For some reason, the most exciting element of projection selection is often overlooked by cartographers.
If you think of choosing a projection type as you would choosing a camera lens (e.g., fish-eye versus panoramic, etc.) then choosing an orientation and zoom level is the equivalent of framing your shot in photography.
Let’s start with orientation. Instead of thinking of this as you learned it in your GIS class — oblique, normal, transverse (briefly reviewed in the video at the end of this post) — it’s better to approach map orientation like a filmmaker or photographer. The perspective you use to highlight your projection will determine not only what can be seen but how it will be interpreted.
There is far more to orientation than the boring-as-hell academic crap in textbooks. It’s important to understand those concepts at a rudimentary level, but when it comes to effective design and communication, we can learn more from the visual arts than GIS.
Indeed, photography and film show us that we can use orientation to make different arguments and tell different stories. You can focus on one area over all others or you can use orientation to tie different areas together within your communication (e.g., the Denmark map below).
The two images of the Northern Lights over Norway below result in different feelings and messages to the viewer.
Orientation (or camera perspective) allows us to do the same thing with our maps. In the four images of Somalia and the Indian Ocean at the start of this post, orientation and projection were changed to frame the same scene differently.
Fortunately, map orientation is really easy to tweak in most GIS software. The video here shows how to do it in ArcMap in under 30 seconds.
Zooming in on a map to limit what can be seen to a particular area of interest also limits your map viewer’s imagination of the scene. And that’s a good thing. It’s the ultimate form of map generalization!
Eliminating areas from people’s consciousness is key to storytelling. Filmmakers do this with their cameras. Cartographers do this by selecting an appropriate map extent!
Filmmakers leave out the boom mics, the water coolers, and the fact that what you’re seeing is actually nothing more than a warehouse full of set furniture.
Cartographers cut out everything that is irrelevant — like the UK on a map of the EU. (Sorry to my European and British friends… Too soon?!)
In the images of the Indian Ocean at the start of this post, the map reader can be distracted by a variety of outside influences — thoughts of southern Asia, the Persian Gulf, the Horn of Africa, Indian Ocean vacations… etc.
Another chief goal of a cartographer is to make sure map readers “suspend their disbelief.” This also relates to filmmaking… and oddly enough, professional wrestling. The best movies, the most effective films, are those where you are able to stop thinking critically about the fact that it’s make believe… it’s not real.
You know that you can’t hear sound in space, that the Millennium Falcon isn’t aerodynamic enough to enter orbit at light speed and not disintegrate, and that stormtrooper armor would require soldiers who never have to urinate. You don’t care while watching the film. You eat up the story and are willing to suspend your disbelief.
The following base map of Denmark would be a useful orientation if you were hired to highlight Denmark as the keystone of Scandinavian and Nordic cultural strength. (This is a total hypothetical just to make my friend Klaus in Aarhus laugh and irk Mette in Tromso.)
The areal extent and orientation of the projection give you no choice but to focus on Denmark. Germany is basically omitted. A majority of Sweden and Norway are truncated. Finland left out, because there is still little consensus whether it is part of Scandinavia anyway.
The parts of Scandinavia that remain are relegated to the map’s periphery. Denmark “uber alles” — or at least uber Scandinavia — this base map screams! With the right visual variables, you may even convince people to buy into this argument.
Quick Side Note on Above Professional Wrestling Reference
Suspension of disbelief is why professional wrestling remains popular. (Yes, it really is popular. Check out the WWE stock price and dividends. You’ll wish you invested in 2014 at $11 a share!)
Of course professional wrestling isn’t real! Everyone knows that. But due to exciting story lines and absolutely roided-up, gladiator-esque participants, spectators willingly suspend their disbelief and pay lots of money to enjoy the show.
Projections are complex. Think of them like a filmmaker with her camera, though, and they become extremely empowering in shaping your visual communication.
Below is a 30-minute, turbo-charged lecture on projections to get you up to snuff on the basics. Please look at the YouTube channel for citations to some of the graphics and some of my favorite textbooks covering the cartographic fundamentals of projections.