Editing Decca Navigator System (section)

===D-Day landings===

A three-station trial was held in conjunction with a large-scale assault and landing exercise in the [[Moray Firth]] in February/March 1944. The success of the trials and the relative ease of use and accuracy of the system resulted in Decca receiving an order for 27 ''Admiralty Outfit QM'' receivers. The receiver consisted of an electronics unit with two dials and was known to its operators as the "Blue Gasmeter Job". A Decca chain was set up, consisting of a master station at [[Chichester]] and slaves at [[Swanage]] and [[Beachy Head]]. A fourth decoy transmitter was located in the [[Thames Estuary]] as part of the deception that the invasion would be focussed on the [[Calais]] area.
21 minesweepers and other vessels were fitted with ''Admiralty Outfit QM'' and, on 5 June 1944, 17 of these ships used it to accurately navigate across the [[English Channel]] and to sweep the minefields in the planned areas. The swept areas were marked with buoys in preparation for the [[Normandy Landings]].

After the initial ship tests, Decca conducted tests in cars, driving in the [[A3 road|Kingston By-Pass]] area to verify receiver accuracy. In the car installation, it was found possible to navigate within an individual traffic lane. The company entertained high hopes that the system could be used in aircraft, to permit much more precise navigation in the critical airspace around airports and urban centres where traffic density was highest.