Pigboat, thats right, it was the first of the parabolic nav aids that were subsequently used into the sixties I believe.. .. .Loran was another which I think came into use sometime after Gee. Postwar Decca developed a civil version which saw some use and even a long range version which was good for trans atlantic use, but this never caught on.. .. .In UK in the 50's we used to do Gee approaches with the mark3 version which could be quite accurate depending how well aligned the runway was with one of the Gee lines.