Google Maps is surely the most accurate mapping service on sale now or ever made – even if I find its iPhone app palpably annoying to figure out – but as well as all its technology, it has people. Some drive those dinky cars you’ve seen. Others change the maps under their fingers.

It’s an example of just how much you can do when you have a lot, I mean a lot, of data gathered from everyone and everywhere around you.

The maps we use to navigate have come a long way in a short time. Since the ’90s we’ve gone from glove boxes stuffed with paper maps to floorboards littered with Mapquest printouts to mindlessly obeying Siri or her nameless Google counterpart.

The maps behind those voices are packed with far more data than most people realize. On a recent visit to Mountain View, I got a peek at how the Google Maps team assembles their maps and refines them with a combination of algorithms and meticulous manual labor—an effort they call Ground Truth. The project launched in 2008, but it was mostly kept under wraps until just a couple years ago. It continues to grow, now covering 51 countries, and algorithms are playing a bigger role in extracting information from satellite, aerial, and Street View imagery.

The Huge, Unseen Operation Behind the Accuracy of Google Maps – Greg Miller, Wired (8 December 2014)

Read the full piece for more.