Michael,
I seem to remember that one Scout in the squadron had Dectrac fitted. I can remember using it one New Years Eve over Armagh ( 1974 I think) Since it was such a clear night and we could see the lights of of the town and the next town it wasn't of great use. As I remember it it gave you the red, green and purple lanes which had to be plotted on a Decca map. Strictly a two man operation.