They say you should never learn how the sausage gets made, but we're willing to make an exception for Google Maps. Talking to The Atlantic, Google has revealed just how much the human element figures into all that collected satellite imagery and road data. Many pieces of terrain information are tested and modified against what Google calls Ground Truth: actual driving, alternate sources and sign photos automatically extracted from Street View runs. Google isn't just making the occasional correction, either. Mapping a country can take hundreds of staff plugging away at the company's Atlas tool, even before we get a crack with Google Map Maker. The combination of man and machine helps explain why Google Maps is one of the most accurate sources of location information on Earth -- although the firm does have some catching up to do in space.