GPS uses satellites which hopefully, were not orbiting the earth in the 1940's. I believe you're referring to earlier technology used in shipping where multiple radio signals encoded with a timecode were triangulated to give the ships position (a technology still in use today by the russian and american navies, although only as a backup to GPS) and I don't believe this tech either was available in the 1940's. Radar certainly was and operators could radio the pilots to help them through foggy conditions etc
Edit : I really need to think before I write if I'm on topic. There's forums on the web where you get burnt alive for that kind of thing.
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