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Serendipitous Discovery in Visualization

Assuming you couldn't read the city names, can you guess which of these adjacent countries is wealthier (their population densities are similar (78.43 vs. 108.09 people per square km))?

road_density.jpg

While browsing Google Maps in the course of planning for a recent trip I was struck by the greater density of roads in France versus Spain. My best guess is that it's a reflection of wealth (France's GDP is just under twice that of Spain, with only 50% more population). It's interesting to me that information that's not encoded in the maps can nonetheless be inferred from them. First-rate visualizations allow us to see patterns and draw conclusions that are not only hidden in raw data, but are qualitatively different from the data itself. To be trendy (or clich├ęd) I could call it an emergent quality of data visualization.

Another example is the city lights data from NOAA and NASA:
lights_excerpts.jpg

The economic disparity between North and South Korea, the split in the Trans-Siberian railroad as it goes around Lake Baikal, and the cities and towns clustered along the Nile River are all features that fall out of the data display. I'd be interested in other examples, so feel free to comment.

Comments

This examples are pretty interesting. I suspect that it is worth adding a little more precision to the infered statements, however, With the lights, one can see which countries *spend* more on lighting. This distinction is important to make, for example, when one considers that recent studies in Japan have indicated the amount of light wasted (by being sent out in to space). Hopefully this type of study will result in policies that reduce the amount of wasted light.

The roads example might also need to take into consideration policies regarding public transport spending (e.g. rail) versus infrastructure for private transport (more likely to be roads).

These are subtle differences, but important when making inferences - making the assumptions clearer.

To be fair, in the screenshots there is no visible scale-factor mentioned, so the 2nd image could be of a much larger area than the 1st, creating the illusion of a denser road-network.

Or it could mean that the French have way too much time on their hands and like to build roads in their free/spare time :)

You're right, they need a scale. I first noticed the difference with all of Spain and most of France visible on screen, but I had to make the crops to fit in the relatively narrow blog column, and I tried to crop out anything that would immediately identify each country (i.e. Madrid or Paris), then never put the scale back in.