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(Navigation) trademark an electronic navigational aid in which the image of a ground-based radar system is televised to aircraft in flight so that a pilot can see the position of his aircraft in relation to others
[C20: from Tele(vision) R(adar) A(ir) N(avigation)]
(sometimes cap.) a navigational aid that uses radar to map the sky above an airfield, which, together with a map of the airfield itself, is transmitted by television to aircraft approaching the field.
[1945–50; short for tele(vision)r(adar)a(ir)n(avigation)]