At any given moment, our mobile devices are taking stock of us—our GPS coordinates, our clicks, our habits. Much of the time, this has nothing to do with self-knowledge, and everything to do with the data being bought and sold in marketplaces several times removed from what we see on our screens.
Sometimes, though, that data is given back. Take, for instance, this heat map of 220 billion GPS coordinates that gel into running and cycling hotspots all over the world. Fitness app Strava, which works on roughly 100 devices (including Garmin, TomTom, and Timex), uploaded public running data from its users into a set of nearly 78 million bike rides and 20 million runs. Zoom in, and you can see the spray of individual pings from people’s devices.
This kind of map can come in handy in a few ways. On the most basic level, it helps runners and cyclists choose routes—the app itself leads users down paths that have been used by other runners and cyclists before, maybe avoiding bad intersections, or roads without bike paths. But this type of data can also help urban planners. If a popular bike route doesn’t have bike lanes, a map like this could help planners prioritize new paths. The hotspots also show which areas are most valued by cyclists and runners—and which bits of infrastructure, perhaps, deserve more attention from local government.
Strava users also have the opportunity to opt out if they don’t want their data being uploaded to the global heat map. If you’re running in rural Idaho, for example, you might not want just anyone tracking your single set of GPS coordinates in the hinterlands. In aggregate, though, these maps display a pattern of human activity that’s simply mesmerizing. Also, if you ever go on vacation to the southern tip of Chile, you now know where to go for a run.