The cone of uncertainty is a core feature of hurricane maps: it shows the potential routes a hurricane is likely to take (the path grows over time, as we’re less certain where the storm goes next). But it’s misinterpreted in ways that put people at risk. That’s the argument made by Alberto Cairo in an online infographic (and in print) in the New York Times last week: research reveals that people living along the edge of the cone are much less likely to prepare for the storm, even though the edge of the cone is one possible path for the centre of the storm—and the cone only covers 60 to 70 percent of the storm’s potential paths in any event.
So you would like to use a satellite image in your article and you would like to explain it to your viewers? Here is a short guide covering some of the most frequently asked questions and giving some general explanations on satellite images. It by no means covers all aspects, as there are far too many types of satellite images, but should give you a good start to find out more on your own and maybe motivate you to create your own images, which has become quite easy and quick even with no prior knowledge of it.
Complete with examples of imagery, examples of how to use it properly, and links to resources.
The white underlying geographic map places states in their familiar size, shape and location, allowing them to be identified quickly. Using a cluster of dots rather than a solid fill to represent the outcome ensures that the amount of red and blue on the map accurately reflects states’ weight in the election outcome, rather than the (irrelevant) surface area.
Like the tiled grid cartogram, the number of electoral votes in each state is easy to compare visually without counting or interpreting numbers printed on the map. Because each electoral vote is a discrete mark, it is possible to accurately represent the split electoral votes that are possible in Maine and Nebraska, or the possibility of a faithless elector.
Today, print subscribers to the New York Times were treated to a fold-out map showing a choropleth map of the 2012 election results at the ZIP code level (above). “The map is part of a special election section that aims to help explain the political geography of the United States — identifying where people who are conservative and liberal live and pointing out how physical boundaries, like the Rio Grande and the Cascade Mountains, often align with political ones,” writes the Times’s Alicia Parlapiano.
Parlapiano’s piece is in fact a lengthy tutorial on how to read election maps, along the lines of the pages I linked to in last week’s post on election map cartography—it outlines the problems of state-level election maps and choropleth maps that privilege area over population, for example, and shows some other ways of depicting the results.
Alan Smith of the Financial Times adds to the conversation about when to use a map to present your data, when not to—he gives an example where a gridded infographic is a much better choice than a map—and when more than one map is required to tell the whole story. “So as lovers of maps, we are keen to create beautiful ones whenever they offer a crucial addition. Truly appreciating them, however, means not defaulting to a map just because you can. Like a lot of things in the world of data visualisation, the right way to use them is to follow the mantra ‘fewer, but better’.” [WMS]