Where does the data for maps come from?

How is data for maps collected? Firstly for paper-based maps. Secondly for electronic maps? Do they have people who drive every road? Do they take photos from the air? And lastly how do they translate that into electronic maps that can guide you in the car?|||Modern maps are done by aerial photography. If you have ever been driving along and you see a big, white sheet about 40 feet on a side with a big black "X" in the middle, that is a registration mark station. When the photos are put together to make the map, they line up those "X" marks so the map is aligned... then they use another program to develop the linear drawings.