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Whole Earth map based on satellite data. The land is dominated by vegetation (green) or arid land (brown), such as the deserts of North Africa. The polar regions are covered by snow and ice (white) on sea and on land. The map is based on year-long observations by American NOAA weather satellites for cloud-free coverage. Ocean coastal colour (due to chlorophyll content) is provided by the Nimbus 7 weather satellite. The polar regions were imaged with the DMSP weather satellites which are in polar orbits. This map is a latitude-longitude cylindrical projection that distorts and magnifies polar regions relative to equatorial regions. (KEYSTONE/SCIENCE PHOTO LIBRARY/PLANETARY VISIONS LTD)