This image of Earth’s city lights was created with data from theDefense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS).Originally designed to view clouds by moonlight, the OLS is alsoused to map the locations of permanent lights on the Earth’s surface.
The brightest areas of the Earth are the most urbanized, but notnecessarily the most populated. (Compare western Europe with Chinaand India.) Cities tend to grow along coastlines and transportation networks.Even without the underlying map, the outlines of many continents would still bevisible. The United States interstate highway system appears as a lattice connectingthe brighter dots of city centers. In Russia, the Trans-Siberian railroad is athin line stretching from Moscow through the center of Asia to Vladivostok. TheNile River, from the Aswan Dam to the Mediterranean Sea, is another bright threadthrough an otherwise dark region.
Even more than 100 years after the invention of the electric light,some regions remain thinly populated and unlit. Antarctica is entirelydark. The interior jungles of Africa and South America are mostly dark,but lights are beginning to appear there. Deserts in Africa, Arabia, Australia,Mongolia, and the United States are poorly lit as well (except along the coast), along withthe boreal forests of Canada and Russia, and the great mountains of the Himalaya.
The Earth Observatory article Bright Lights,Big City describes how NASA scientists use city light data to map urbanization.
References & Resources
Data courtesy Marc Imhoff of NASA GSFC and Christopher Elvidge of NOAA NGDC. Image by Craig Mayhew and Robert Simmon, NASA GSFC.
