[Bucephalus355]

Tracking / Signal Hunting technology for planes and boats has always seemed to generate the most fantastical ideas.

There has been a good amount of progress, but it really stalled for a while when ICBMs seemed to negate the importance of aircraft. The US had the quite sophisticated Northern Early Warning Line at one time to monitor all airspace in the North Pole. It’s very hard, even today, to get good satellite tracking there because it is a Pole.

The craziest thing I’ve heard is what the British tried before radar was invented. A Hoover Dam like wall 200 feet high that was supposed to amplify the sounds of planes approaching from Germany that would alert a human operator.

http://www.andrewgrantham.co.uk/soundmirrors/locations/denge...

[FlyMoreRockets]

RF snooping has traditionally been done by "fishing trawlers".