September 2015 - Cartography
This month, we took a break from the business of data crunching to discuss cartography at Telegraph Beer Garden with Ruth Miller of Guerrilla Cartography.
Part science and part art, cartography acknowledges that reality can be modeled in many different ways. At tonight’s MapTime, we split into small groups to share our experiences with misleading spatial information, and constructive critique the maps of others. We came up with this short list of questions to help create more cartographically honest maps.
All example maps below are from Food: An Atlas.
1) Does the map orient the viewer?
First, consider your audience. Is this a map for your neighbor, guiding them around an area you both know well? Or is it a map for an unknown audience that might reach people outside your field? Take every step to ensure your viewer will know what they’re looking at, and take nothing for granted.
This area should be obvious to someone familiar with Los Angeles, but to a New York resident, maybe not. The inset map of California would be meaningful to most North Americans, but maybe not a person from Malaysia. The mapped area isn’t even depicted on the California map. This map, while beautiful, could spend more time on orientation.
Compare this to the map below, which uses both a relative location map and an inset map boundary. But how many people might get thrown off because they expect land to be shared more darkly than water?
2) Does the data tell a story?
Maps are more than just pretty pictures - they depict data. Compelling maps tell a story about their data.
Consider the map above. It’s essentially a list of locations that produce “Appalachian Grown” products, all around Appalachia. It’s probably accurate, but what does it mean? What questions does it raise or answer?
Compare this to the map below, which identifies the areas of food insecurity among Canada’s First People. Scarcity seems more common in more remote areas. Is this trend consistent across countries? How many of these indigenous people live on land with productive resources? This map inspires further research.
3) Does the map support the story being told?
Public Service Announcement: Friends don’t let friends use the mercator projection. Not only is it inaccurate, it’s effectively racist. By distorting the northern hemisphere to be so large (Greenland appears the same size as Africa, when Africa is actually 14x Greenland’s area), the map makes northern countries look more important. Read this XKCD comic for more.
Back to Food: An Atlas. The text in the map below discusses access, but it doesn’t say much about farmers markets per capita. Looking closely, it actually just depicts farmers market size, not access.
4) Does the map make assumptions?
Dust off your 10th grade World History and look at the world map from 1700.
Where could one possibly find crop and pasture data from 1700 for the New World? Lewis and Clarke didn’t launch their exploration of Western North America until 1804. It’s almost as if the cartographer is saying - if a European didn’t observe crops or pasture, then no agricultural harvest took place.
The cartographer might have had the data to support these assertions, but as presented here, the map makes some uncomfortable claims.
5) How could the map be more readable?
Readable, beautiful, compelling, or simplified. Ultimately, a map has to be understood. Consider font size, color schemes, and projections.
As Edward Tufte would say, try taking out each piece of information one at a time and seeing if the map is better or worse for it.
The map above is undeniably beautiful (look at that Peirce quincuncial projection!). But it has a lot going on. It wisely uses the same scale for county and country production, but the color scheme could be a little less confusing. Do the country-specific inflows really require annotation? Why label California’s counties but none of the countries? No map is perfect, and questioning all of these individual cartographic decisions can simplify the presentation and broaden its potential audience.
In Summary
Cartography is fertile ground for constructive criticism. Question everything, and check your assumptions. MapTime proved a great place to do some peer reviews, and we look forward to holding a second round in the future.
Want to learn more? Pick up a copy of How to Lie With Maps, or subscribe to the Guerrilla Cartography newsletter.