The object of this paper is to summarize the results of air and sea trials that have been obtained in the first two years' operation of the experimental Dectra chain in the North Atlantic area. Reference is also made to observations at fixed monitor stations, and briefly to the Dectra data link for air-to-ground transmission of the Dectra fix.

Dectra, which stands for ‘Decca Track and Range’, is a long-range position-fixing system derived from the Decca Navigator. Early in 1957 two of the three transmitting stations forming a Dectra chain designed to cover the North Atlantic air routes were put into operation and flight tests began in March of that year; in the following October, air trials started using all three transmissions. Various tests at sea have also been carried out, although on a much less extensive scale than those in the air.