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How Google builds its maps

The Atlantic's Alexis Madrigal looks into how Google builds its maps.

Behind every Google Map, there is a much more complex map that's the key to your queries but hidden from your view. The deep map contains the logic of places: their no-left-turns and freeway on-ramps, speed limits and traffic conditions. This is the data that you're drawing from when you ask Google to navigate you from point A to point B — and last week, Google showed me the internal map and demonstrated how it was built. It's the first time the company has let anyone watch how the project it calls GT, or “Ground Truth,” actually works.

… I came away convinced that the geographic data Google has assembled is not likely to be matched by any other company. The secret to this success isn't, as you might expect, Google's facility with data, but rather its willingness to commit humans to combining and cleaning data about the physical world. Google's map offerings build in the human intelligence on the front end, and that's what allows its computers to tell you the best route from San Francisco to Boston.