If I may let the decca drift us slightly off-thread
, when I was flying Wessex we had 1" O.S. maps with Decca overlay. It was quite feasible to make an approach to Odiham, using (IIRC) the green 30 line for left/right and the purple lines for range, with the other pilot calling out the ranges and recommended heights. Of course, that always assumed he knew his left from his right!
OK, back on thread.