Description text

To obtain high-resolution imagery, Google Earth uses DigitalGlobe's QuickBird satellite to photograph the planet's surface at an altitude of 450 kilometers. The average resolution is roughly 60 square centimeters per pixel if the satellite is looking straight down, or less if it is looking at an angle. But because the satellite makes only 15 orbits per day, and because there is huge competition for its camera, most regions of the planet have not been photographed at high resolution; an example is Hazelton, WV (left). Lower-resolution data is provided by other satellites, such as the Landsat-7, which has imaged the entire planet at a resolution of 15 meters.