OpenStreetMap is a marvel of modern crowdsourcing. Since its creation in 2004, DIY cartographers – typically armed with GPS devices or satellite photography – have been slowly mapping the world's road networks and landmarks to create a free alternative to proprietary geographic data that can then support tools like trip planners. The process, which began in the U.K., is painstaking and piecemeal, and nearly a decade into it, more than a million people have contributed a sliver of road here or a surveyed cul-de-sac there.
Academics refer to this kind of collaborative mapmaking as "volunteered geographic information," and OpenStreetMap is one of the most successful examples of it out there. Research into the system suggests that these amateur maps are impressively accurate in communities dense with contributors (like Germany: Germans love OpenStreetMap). But until now, it's been much easier to assess how good these maps are than to ask how they got that way.
Now, researchers are getting much better at processing OpenStreetMap's data to access its history. The above historic timelapse comes from a study, published in the journal Spatial Statistics, that retraced the growth of OpenStreetMap networks in three areas of Ireland to understand how the networks are built.