Saturday, August 25, 2012

Multiple shapes, multiple projections

A few days ago, I tweeted about the beautiful map above, Hurricanes and Tropical Storms since 1851. I added a short note about the projection, which may be unusual for someone who was born in Europe, the US, or Continental Asia, as it is centered on the South Pole. Rob Simmon, a data visualizer at NASA Earth Observatory, replied: "I disagree with the map projection choice, far too much distortion of the data, especially in the Northern Hemisphere." That's a legitimate concern. Distorsion is a major challenge when designing maps.

I gave Rob's comment some thought, as it is somehow related to the core idea in The Functional Art: Information graphics are tools; before choosing visual shapes to encode data we should define the tasks our graphics should help readers with. Additionally, in interactive visualizations we may want to explore information from different angles. In the video lectures that you get with the book, I point out that designers usually forget that sometimes it may be necessary to represent data more than once, with different kinds of charts, maps, and diagrams, each adapted to a particular function.

I've applied this idea in the past. For instance, in this interactive graphic about world population since 1950. Click on the "Mapa" tab to begin:

In that piece, you can switch between a proportional symbol map, a set of line charts (click on any bubble and use the menu there to add more countries), and a table in which the data can be filtered and sorted. Each one of those graphic forms has a different goal. After all, the bubble map offers an overview, the big picture, but it doesn't let you compare countries, rank them, or see population change with precision.

Back to IDV's hurricane map, let's dream a bit: What about if we made it interactive and we allowed visitors to change its projection, so they can visualize the blue paths in different ways? Would that be helpful? Rob Simmon suggested then that I should try NASA GISS, a wonderful little app with tons of world map projections. I think I will use it in class eventually, when the time comes to explain the basics of cartography to my University of Miami students. See some screenshots: