It’s an increasingly common navigational experience in the age of connected and app-enabled phones: you can see yourself as a little dot on the map, moving on your screen as you move in the physical space of the world. You see your map, your map sees you. And if your map is a Google Map and your screen powered by the Android operating system, you can see your map seeing you and many of the people around you.
This collection and sharing of locational information is the basis behind the traffic-tracking layer on Google Maps. By combining all those devices’ location points and detecting the speeds at which they’re moving, Google is able to infer how quickly traffic is moving on major streets and highways. Originally launched in 2008, it can be a really useful layer of urban information, representing real-time conditions.