Science: Doppler Reckoning

When oldtime ships' officers could not see the sun or stars, they fell back on dead reckoning. By recording the ship's direction and its motion through the water, they tried to keep track of its position. The system did not work very well, chiefly because of crude instruments and because the effect of ocean currents was often unknown. But if a ship could have measured accurately its motion across the solid ocean bottom instead of the fluid surface, dead reckoning would have brought it to any harbor through the thickest fog.

The Navy's automatic navigator AN/ANP-67, which was publicly described in detail...

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