Google Maps is a huge project involving AI, computer vision, big data, and lots of physical hardware and people.  At the recent Google I/O event, they discussed one project “Ground Truth” that constantly refines the data to ensure accuracy and relevance.

For example, Google might get road information from a government that indicates a particular road is a two-way street. But Google’s own traffic data, gathered anonymously from people’s Android phone data, might show that it appears to be a one-way street. A Ground Truth operator then can look at Google Street View data, including signs, to see what’s actually there, he said.

via With Ground Truth, Google marries virtual world with the real | Internet & Media – CNET News.