In the early 1960s, maps of the shape and depth of the seafloor were largely hand-drawn, based on sonar sounding profiles along the ship track of each survey voyage. All these depended for accuracy on knowing the position of the survey ship. Ships today use global positioning systems, but then sailors used traditional sightings on the Sun or stars, and dead reckoning. In poor weather with cloudy skies for a week or two, the ship position could easily be out by tens of km. Satellite navigation began when US Navy launched its transit satellites in the early 1960s. Sea-borne gravity meters were used in the early 1960s, as were magnetometers; the latter had to be towed on a line a few hundred metres long, to avoid the ship’s own magnetic field. LamontLamont Geological Observatory (now Lamont-Doherty Earth Observatory) was established by Columbia University, New York in 1949 following a gift of land by the Lamont family. Maurice Ewing was its first director and his dedication to exploration and discovery established it as a world leader in geophysics. Ewing demanded comprehensive data collection on Lamont research voyages, building a vast store of data: the Vema alone covered more than a million miles in her working life at Lamont. Despite this, Ewing and his colleague Walter Bucher did not accept the mobilist worldview of plate tectonics. ships, in particular, routinely recorded the magnetic signal while at sea, providing a vast library of data across the world’s oceans. The Vine-Matthews-Morley conveyor-belt modelthe test of symmetrical sea floor spreading theory relating to continental drift. for the formation of magnetic anomalies during seafloor spreading made sense of the data; the oceans then became a key to reconstructing the geological history of the planet.