Maps do not just reflect reality; a new online exhibit at the Boston Public Library looks at how they help shape reality:

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The original topic was to do an exhibition of a classic category of maps called persuasive cartography, which tends to refer to propaganda maps, ads, political campaign maps, maps that obviously you can tell have an agenda. We have those materials in our collections of about a quarter million flat maps, atlases, globes and other cartographic materials. But we decided in recognition of what’s going on now to expand into a bigger theme about how maps produce truth, and how trust in maps and other visual data is produced in media and civil society. So rather than thinking about just about maps which are obviously treacherous, distorting, and deceptive, we wanted to think about how every map goes about presenting the world and how they can all reflect biases and absences or incorrect classifications of data. We also wanted to think about this as a way to promote data literacy, which is a critical attitude towards media and data visualizations, to bring together this long history of how maps produce our sense of reality…

We commissioned a special set of maps where we compiled geographic data about the state of Massachusetts across a few different categories, like demographics, infrastructure, and the environment. We gave the data to a handful of cartographers and asked them to make a pair of maps that show different conclusions that disagree with each other. One person made two maps from environmental data from toxic waste sites: One map argues that cities are most impacted by pollution, and the other says it’s more rural towns that have a bigger impact. So this project was really meant to say, we’d like to think that numbers speak for themselves, but whenever we’re using data there’s a crucial role for the interpreter, and the way people make those maps can really reflect the assumptions they’ve brought into the assignment…

In one section of the show called “How the Lines Get Bent,” we talk about some of the most common cartographic techniques that deserve our scrutiny: whether the data is or isn’t normalized to population size, for example, will produce really different outcomes. We also look at how data is produced by people in the world by looking at how census classifications change over time, not because people themselves change but because of racist attitudes about demographic categorizations that were encoded into census data tables. So you have to ask: What assumptions can data itself hold on to? Throughout the show we look at historic examples as well as more modern pieces to give people questions about how to look at a map, whether it’s simple media criticism, like: Who made this and when? Do they show sources? What are their methods, and what kinds of rhetorical framing like titles and captions do they use? We also hit on geographic analysis, like data normalization and the modifiable area unit problem…

So rather than think about maps as simply being true or false, we want to think about them as trustworthy or untrustworthy and to think about social and political context in which they circulate. A lot of our evidence of parts of the world we’ve never seen is based on maps: For example, most of us accept that New Zealand is off the Australian coast because we see maps and assume they’re trustworthy. So how do societies and institutions produce that trust, what can be trusted and what happens when that trust frays? The conclusion shouldn’t be that we can’t trust anything but that we have to read things in an informed skeptical manner and decide where to place our trust.

Another reminder that data does not interpret itself. Ordering reality – which we could argue that maps do regarding spatial information – is not a neutral process. People look at the evidence, draw conclusions, and then make arguments with the data. This extends across all kinds of evidence or data, ranging from statistical evidence to personal experiences to qualitative data to maps.

Educating the readers of maps (and other evidence) is important: as sociologist Joel Best argues regarding statistics, people should not be naive (completely trusting) or cynical (completely rejecting) but rather should be critical (questioning, skeptical). But, there is another side to this: how many cartographers and others that produce maps are aware of the possibilities of biased or skewed representations? If they know this, how do they then combat it? There would be a range of cartographers to consider, from people who make road atlases to world maps to those working in media who make maps for the public regarding current events. What guides their processes and how often do they interrogate their own presentation? Similarly, are people more trusting of maps than they might be of statistics or qualitative data or people’s stories (or personal maps)?

Finally, the interview hints at the growing use of maps with additional data. I feel like I read about John Snow’s famous 1854 map of cholera cases in London everywhere but this has really picked up in recent decades. As we know more about spatial patterns as well as have the tools (like GIS) to overlay data, maps with data are everywhere. But, finding and communicating the patterns is not necessarily easy nor is the full story of the analysis and presentation given. Instead, we might just see a map. As someone who has published an article using maps as key evidence, I know that collecting the data, putting it into a map, and presenting the data required multiple decisions.