If I give someone a map and they talk about the map more than the data, I have failed.
~Kristin Warry, GISgroup, LinkedIn

Assuming your map audience isn’t cartographers*, this statement is a perfect way to describe how effective map design should be in most cases: extremely usable. It takes very good design skills and a lot of time to make a map that is so useable that people forget about the mode of communication and listen only to the message.

Some of the best examples of informative and non-showy mapping come from the New York Times. Here are a few:

Hurricane Irene Damage Map

Joe Burgess, Amanda Cox, Alicia Parlapiano, Archie Tse, Lisa Waananen, Tim Wallace

Mapping America, Census Map

Matthew Bloch, Shan Carter, Alan McLean

Super Bowl 2011 Twitter Chatter Map

Matthew Bloch and Shan Carter

* If you show a map to cartographers, of course they’ll talk about the map design. A few other exceptions exist as well, such as when a map is made primarily for advertising purposes, in which case it may be more beneficial to make something outlandish that attracts attention first, and is useable, second. Another exception is brand-new map design inventions, which may take a while for people to become accustomed to before they pay attention the actual data (e.g., subway map style, the recent facebook friendship map.)

This map of The World’s Newspapers * has some nice things going for it:

The first thing that we notice is that it isn’t over-styled. All the blue tones are muted, the red circles don’t have any casings (they stand out enough on their own without being outlined), there aren’t extraneous details like ocean colors or labels, and the authorship information and date are readily available.

It appears as though the mappers decided not to delineate each county with an outline, though I think that they might have done well to have considered doing so. It’s odd that only the No Data countries have outlines. Other than that, seems like a nice, simple, effective map for it’s purpose, audience and medium.

*By Dr. Mark Graham, Scott A. Hale and Monica Stephens in collaboration with Dr Corinne M. Flick and the Convoco Foundation.

Think about your audience when designing your maps. For example, at the California Academy of Sciences yesterday I noticed that the maps in the rainforest exhibit were both extremely simple and extremely effective. The rainforest exhibit is comprised of several stories wherein each represents typical species you would find in each of three or four country’s rainforests (Borneo, Costa Rica, for example). Each level had a map at the beginning to show you where, for example, Borneo is.

The maps are just landmasses of the earth and a simple square around the general region. There wasn’t a need for labeling of major countries or hillshading or aerial photography or anything that would take away from the very simple message. Now, there are a lot of times when there is A LOT more needed on a map than landmasses and a locator box, but the designer adroitly regarded anything other than the basics to be superfluous and, quite likely, distracting from the exhibits.

Now, mind you, these maps are not pieces of art that someone’s going to take a picture of themselves next to. But then again, I noticed they were used quite a bit for actual spatial-knowledge purposes!

I’ve been critiquing a lot of maps lately and keeping notes on common pitfalls as well as ways to earn extra viewer “points”. * Here are those notes. Keep in mind that the maps that inspired these recommendations were all of a specific type. This means that the list of pitfalls and extra points is certainly not exhaustive.

PITFALLS

• Watch out for region boundary lines that are too thick. If you have country outlines on a world-wide map or state outlines on a country-wide map, for example, make sure they are visible, yet not overwhelming. You can make them white if the background is dark or gray if the background is light. Make them just thick enough to be visible.
• Labels should not cross lines where possible. If it can not be avoided, try putting a halo around the label to obscure the line underneath the label. If the line shows up underneath the letters it gets muddled up with the typography.
• Be wary of your font choice in large blocks of text. If there are more than two lines of text grouped together with more than, say, five words on each line, a serif font is a fresher choice than a sans-serif. If insisting on a sans-serif then look for something with a bit of flow and character.
• Run the map by someone else and ask them to tell you if there are enough labels on the map. For example, you might think everyone knows that the inset map shows Hawaii but not everyone does.
• Try not to have more than five gradations of a symbol size. This is because it is difficult for the human eye to discern differences in symbol sizes at a greater number than that. Think about how hard it would be to determine what a certain circle means if there are 12 different circle sizes on the map. If you really want that many circle sizes, then make it clear that the viewer doesn’t need to know what it represents exactly by making the legend reflect that. This can be accomplished by only showing the smallest symbol size and the largest symbol size with a line in between, for example.
• When using circles to pinpoint a great many locations on a map, don’t use circle casing (the extra bold circle outline) as it just adds clutter. If there are only a few locations and you need some extra pop then it is acceptable.

EXTRA POINTS

• Dig in to the details of the data you are portraying. If you can unearth some conclusions that aren’t readily apparent via the spatial representation, then consider illustrating these via graphs or extra text-blocks.
• If your map makes someone else say, “Oh, how neat” then you’ve probably done a good job.
• If there are large areas of a single color taking up more than 1/4 of the page, consider using a gradient fill. For example, a map of Colorado historic sites could incorporate a brown background that starts out darker at the northern border and ends up lighter at the southern border. (Make it subtle.) Of course there are lots of other ways to do backgrounds including subtle hillshading and aerial imagery but keep this one in mind too.
• You get major extra points for highly skilled incorporation of the margin elements. Think graphic-design. Sure, it is good to evenly distribute and group elements around the main map. But it is even better if those elements become a part of the overall feel rather than just hanging out around the main event. I’m thinking of unique style choices like copyright text that curves around the globe, a legend that blends in to the border, and such. If you don’t have any ideas of your own then make an effort to look at several maps on the Web, noting unique style choices that you could use.

*Pitfall! was a very succesful Atari game made by Activision. The main objectives were to keep from falling in quicksand, water or tar pits by swinging on jungle vines and earning extra points by collecting treasure.

The first weather map was published by Sir Francis Galton in the London Times in 1875.

The New York Times published a map of flooding along the Mississippi and Ohio rivers that is quite nice. Of note is the scale bar at the top which is unlike any I’ve ever seen. It is simply a thick black line with “50 miles” written right-justified underneath. There are no ending marks along the line. A very simple construct that works just fine. One small issue in the map is the leader lines, of which there are two, that point to items on the map that require further explanation. These leader lines are the same color and almost the same weight as the state lines and thus can be confused. This is a minor point as the rest of the features work well together. The colors are muted and logical and the extreme vertical nature of the map is not cumbersome as it could have been. Overall a very nice map graphic.

Flooding Along the Mississippi and Ohio Rivers