Yeah I've not researched it and people are meming about it already and either already know or are pretending to know what it is.
Discussion
What I would do is simply use signal strength of a device you hold as a rough proxy, especially if you can triangulate it.
This is the principle. Checking variation of dielectric constant of moving materials and somehow with a huge amount of data processing extract approximate position of some moving objects.
Easy? Not!
https://hackaday.com/2020/10/22/affordable-ground-penetrating-radar/
No that's the principle behind the noise they discovered under the great pyramids.
It's the same stuff. Radar imaging. Different frequencies, different resolution.