National Geographic : 1962 Aug
True-motion radar set (below) guides Savannah safely through fog or darkness, giving a chartlike picture of the ship's own motion in relation to land and nearby vessels. Ordinary radar requires triangulation to plot speed and course of oncoming craft. ing the scene on the upper screen, Savannah'spilot grease-pencils a bearing line between the ships' blips. Moments later he draws another. Parallel lines on middle scope foretell a collision at X. Lower scope records Savannah's turn to avoid a crash. Shore lines, as traced by radar's line-of-sight view, give a true picture of the ship's surroundings.