Google has attracted a lot of attention for its vehicle-mounted cameras, but these only collect imagery for the Street View feature in Google Maps. The aerial shots in the Maps tool and in Google Earth come from a combination of airplane cameras and satellite images.
Aerial images of cities in Google Maps are usually at a higher resolution than rural areas, deserts and oceans. The city images come from airplanes that fly over the area at between 800 and 1500 feet. These are updated on a rolling cycle for enhanced accuracy: Google says the majority of the images are between one and three years old. In the early years of Google Earth, some of the images came from sources such as hot air balloons, model planes and kites.
Lower resolution images on Google map services come from commercial satellite operators. They send special satellites into orbit that are a cross between a large telescope and a digital camera. Despite orbiting 600 kilometers from earth, the cameras take images at a level of detail that can identify objects as small as 25 centimeters across. However, this level of detail is available only to the U.S. government; companies such as Google are provided a resolution that makes 50 centimeter objects visible.
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