In an article by Mark Aubin, founder of Keyhole, the company that became Google Earth, Aubin said that Google Earth uses more than one source for our imagery.

“We collect it via airplane and satellite, but also just about any way you can imagine getting a camera above the Earth’s surface: hot air balloons, model airplanes – even kites.”

After the raw data arrives the next step is processing the imagery. “We scan the film using scanners capable of over 1800 DPI (dots per inch) or 14 microns. Then we take the digital imagery through a series of stages such as color balancing and warping to produce the final mosaic for the entire area.”

The next step in the process is to add layers of information – things like country and state borders and the names of roads, schools, and parks — to make it more useful. This information comes from multiple sources: commercial providers, local government agencies, public domain collections, private individuals, national and even international governments. Right now, Google Earth has hundreds of terabytes of geographic data, and it’s growing larger every day.