[Joel_Mckay]

There were commercially available lidar/ladar sensors that can do basic spectroscopy at a great distance. Specifically, the public specification showed it was able to pinpoint C02 or nitrate levels over 14km away.

Keep in mind this was published over a decade ago, and I'm sure they have systems with better specs these days. Too bad these were too cost prohibitive for FSD automotive platforms.

There are magnetic sensors that could detect rusting-container currents over 3 meters away, but still unlikely possible outdoors. There is a point where the thermal noise floor means any signal is lost at a minimal threshold.

I am sure folks are extra cautious about detailing key technology these days. =3

[throwthrowuknow]

There are also dirt cheap human presence sensors that use millimetre wave radar that can detect if a person is in the room even if they’re sitting still. If I can buy these for a couple dollars then what could the military do with a few billion dollars and reaper drone platforms? With a big enough array you might be able to pinpoint everything alive within the area under surveillance.

https://www.aliexpress.com/item/1005007989577185.html