>>4815140 (LB)

Actually I didn't mean RF frequencies.

Every phone has a magnetometer which reads deviations in the earth's magnetic field. If you took the readings from a major metro area, cross referenced it to known underground structures, and looked for unexplained deviations, you could make a map of unknown underground structures.

Then task a MAD aircraft/satellite to do a detailed survey.

It's free mapping, crowdsourced. Explains how stuff has been supposedly found under cemeteries etc.

>>4815268

I think we all do. But, if planefags spot SH-60 helicopters over spots, this could be confirmation that they're using Magnetic Detection Arrays to take a peek underground. We've been watching P-3s, but not really rotary wing spoopy planes.

>>4815313

I know, it's why I'm a cadet planefag. The P-3 activity fascinates me.

I know the phone ones are hall effect, but with thousands run through an algorithm, I'm sure you could make a solid map.

>>4815358

This fascinates me now… sauce plox?

>>4815472

Thanks, anon.

o7