From NPR's Science Friday, check out this video about how the GIS layer, Blue Marble is created.
"There's artistry to creating the world, according to Rob Simmon, art director of NASA Earth Observatory. NASA's collection of Earth-from-space imagery dates back to the Apollo 8 mission, when astronauts snapped a picture of Earth rising over the moon. Simmon and NASA scientist Gene Feldman explain how the modern "Blue Marble" images are made and how they relate to scientific study of the Earth. (Credits: images courtesy of NASA) Viewed 15072 times. See More Videos
NASA’s iconic images of Earth from space date back to the late 1960s--with snapshots taken by Apollo astronauts. The modern “blue marble” images are captured by machines and they’re not photos--they’re datasets collected by instruments aboard satellites and then translated into imagery here on the ground."