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CompassionateCedar t1_iv9ls4d wrote

Reply to comment by weizXR in Researchers create a Drone That Can 'See Through Walls' With Wifi | At the University of Waterloo recently fixed one up with a scanning device that is the definition of invasive. by chrisdh79

Actually you can use wifi signals to get a rough layout of a room. Not with this kind of setup, you would need a directional antenna.

It’s been demonstrated by a bunch of nerds messing around with a home made radio telescope years ago.

Wifi uses the electromagnetic spectrum. Just like light does. Except it can pass trough walls. So you can use it to “see” into a room but because of the wavelength is so large and it will pass trough a lot of stuff you will mostly see things that are highly reflective to wifi and other sources of electromagnetic radiation with the same wavelength.

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somerandomii t1_ivaa306 wrote

Well water reacts particularly well, and we’re mostly water. So it can be used to track people inside a building fairly well. And because wifi is providing the “active” part of this active scanner, it can be done very covertly. It would be hard to detect that someone is monitoring your building.

But that isn’t what this article is about.

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MrHaVoC805 t1_ivbnzw9 wrote

It's actually pretty easy to see if someone is using WiFi to monitor a building. The hard part is nailing down exactly where they are if it's not inside your building.

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somerandomii t1_ivcd219 wrote

It’s pretty hard if they’re only listening to your wifi strength and not emitting themself.

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MrHaVoC805 t1_ivgl575 wrote

Except for the whole drones being controlled by what's basically WiFi, they use 2.4 and 5ghz frequencies for that and it will be actively transmitting.

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somerandomii t1_ivh45oh wrote

As I said, I’m not talking about the technology in the article. That’s an entirely different use case.

Also autonomous drones don’t need to emit wifi. But you wouldn’t fly a drone around a building to covertly monitor personnel. Drones aren’t very subtle.

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