Communicating with Maps Part 2: Discussing the issues with CaGIS President Sarah Battersby

By Diana S. Sinton

An Exclusive Directions Magazine Series

In the second part of our summer series on Communicating with Maps, Diana Sinton discusses issues and advances in mapmaking with cartographer Sarah Battersby, a research scientist at Tableau Software and currently the president of the Cartographic and Geographic Information Society.

Q: What are some of the key developments that you have seen in cartography in the last decade?

A: I think that one of the most exciting cartographic developments in the last decade is the explosion of online mapping and tools for map design. It’s amazing to think about the huge efforts that have gone into making it easy for people to visualize their spatial data, whether as a Google Map mashup, using desktop or online GIS, with d3 or other scripting libraries, etc. The downside to all of this is that I think it is still too easy to make a bad map, and way too easy to distribute that bad map to a wide audience. My cartographic archive of what not to do just keeps growing thanks to all of the great finds on Twitter and Facebook.

On the other hand, there are a lot of people who really care about helping others work with and understand spatial data and there is some great research in cartography, GIScience and in spatial thinking that I think will help shape the next generation of tools that we use to design maps to make them more intuitive, more beautiful and generally more effective for understanding spatial data.   

The growth of the open source geospatial community has also been impressive. It is exciting to see so many people dedicated to improving the world of geospatial data and technology, and to helping the world with geospatial, like the work coordinated by the Humanitarian OpenStreetMap Team.  I think this open source momentum is key in the future of cartography and GIS.

Q: People often bring up the issue that Web Mercator is used as a default projection with web maps. That creates a tension with all of us who were taught in cartography and GIS classes that the Mercator projection is almost always inappropriate for the maps we’re making; it grossly distorts areas toward the poles and is presumed to give people false ideas about the size of countries and even continents. How much of a problem is this really? Can we cross fear-of-Mercator off of our worry list?

A: A few years back I did a bit of “forensic cartography” research on this to try to figure out how Web Mercator became the standard, and I think it is because of the success of Google Maps — the projection is even occasionally referred to as “Google Mercator.” Other online mapping systems changed projection to match. I’m not sure what the logic was behind the original selection of the projection, but it is easier to tile a rectangular projection, and the equations for Mercator are simple.  The conformal property of the projection is also nice for local-scale mapping.  But…is it the only choice? I imagine that any rectangular projection should tile nicely, and I imagine that it won’t be too many years before we have online mapping systems that don’t tie us to a single projection. For instance, Bernie Jenny has done some amazing work with adaptive map projections.

As for the distortion in the Web Mercator projection, I think this is a significant issue for visual analysis.  I’m a big believer in one of Egenhofer and Mark’s principles of Naïve Geography, that “maps are more real than experience.” I have thought of this as the map becoming our source of truth; even if people know that there is distortion in the map I think there are very few people who can successfully compensate for it in reading the map. This is a significant problem for any distance or area-based analyses calculated in Web Mercator coordinates, as well as for the map reader trying to visually make sense of spatial patterns.

I definitely wouldn’t cross Web Mercator off of our list of things to worry about. It is imperative for map designers to be actively thinking about and addressing issues with projection, otherwise their analyses may be hugely incorrect.It is also important for map readers to be cognizant of the distortions in Web Mercator and other projections. I don’t mean that I expect people to be able to identify and calculate distortion, just to maintain a healthy skepticism with their map reading.  

Q: What do you think are the top “gotcha” issues for mapping today, from the perspective of a cartographic software designer? What about from the perspective of John Q. Mapmaker?

A: I think that every cartographer has a set of pet issues that they always look for. For me, I often focus on classification and data normalization. It drives me crazy when I can’t figure out how the mapmaker decided to break up the data into classes. Are those quantiles? Natural breaks? Do the breaks have meaning? Class breaks make such a huge difference in the resulting pattern on the map and it drives me crazy when I see the default 5-class natural breaks map without any explanation. To me this is the sign that the mapmaker doesn’t know much about the data.  

I also see way too many maps that are really just population maps. Should it be a surprise that locations with more people tend to have higher counts of all sorts of other attributes? This is another problem of not thinking enough about the data. If you don’t know your data well, how do you make a map that tells a clear — and appropriate — story? 

Q: You have the perspective of having taught students about mapmaking for many years, and have done much basic research in cartography. Now you are in the position of working with software designers to help them implement good mapmaking principles to help users of commercial software design more effective maps. How is this shift from basic to applied research working? How has it changed how you pose research questions?

A: It is great to focus on specific, applied problems tied to facilitating how people ask and answer spatial questions. There is still much to think about in terms of general cartography, but now that we’re at a time when it is so easy for anyone to take a dataset and turn it into a map, I think about what we can do to help people make better maps faster. My research has always focused on how people understand and use spatial data, so there hasn’t been a change in my research direction, but I have done a lot of stepping back to what I would call the “cartographic primitives.” Lately I’ve been doing a lot of thinking about very basic questions of what information we need to obtain from maps and what characteristics of a map would facilitate finding answers to these questions. I also spend a good bit of time thinking about what makes an interesting pattern on a map and how I can help someone make better choices about their map type, colors or classification to uncover these interesting patterns.

Essentially, I feel like the questions I face now are based on how we can take our collective research and applied knowledge about designing better maps and put it to use helping people that don’t have decades or even semesters of work in cartography. It’s an amazing challenge and hopefully I can do some good to help the world see and understand their spatial data more effectively.

Our exclusive series, Communicating with Maps:

Communicating through Maps Part 1: Exploring the challenges and complexities of GIS mapping 

Communicating with Maps Part 2: Discussing the issues with CaGIS President Sarah Battersby

Communicating with Maps Part 3: Considering uncertainty and error

Selected References for Communicating with Maps

Published Wednesday, June 17th, 2015

Written by Diana S. Sinton

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