Topographical relief map of the Earth's oceans, 1978.

This map, which shows the main ocean trenches, was prepared using altimeter data from the Seasat oceanographic satellite. Seasat was launched on 27th June 1978 and carried experiments to measure sea ice, sea surface profiles and wave heights. The satellite was managed for NASA by Caltech's Jet Propulsion Laboratory (JPL) and was designed to circle the globe 14 times a day, providing coverage of 95 per cent of the oceans every 36 hours.