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Comment by jschwartzi | Hacker News Reader

Was this article paid astroturfing for the Drone Defender?

It made some vague allusions to that product's market and then suggested that federal regulations would prevent the sale of it to local law enforcement, but I didn't see any real argument for why local law enforcement should be able to buy jammers other than some isolated incidents in prisons. There also wasn't any explanation for why the FCC and FAA have the rules about jamming. I suspect devices like the Drone Defender are banned for good reason.

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I would think jamming signals on anything flying is a bit on the dangerous side. Yeah some commercial drones will gently land but there's no guarantee. I'd also think it would not take the criminals they are trying to stop long to realize it and find ways around it. Such as preprogramming flight paths in and allowing them to fly without any need to have radio communication.

You might be able to bring a drone in using accelerometers only. Given an assumed measurement error and integration time for the sensor you could calculate how far you'd need to be from the prison before the error in position becomes a problem. So jamming doesn't really buy you anything if you can program a flight path.

I bet you could build a drone that flies off of a visual guidance system using IR beacons to locate itself. Something like a giant version of the Wii's sensor bar.

IR beacons have the downside of blatantly broadcasting their positions, but they might be less jammable than radio waves? OTOH, pointing an IR laser at your camera isn't that hard, so maybe not.

You could also take a page from the SR-71 and correct your inertial guidance system's error using star observations. Only needs to see up, so you can shield it against blinding attempts from below. Can a drone-weight camera pick up stars?

Well a much better way to do optical guidance would be to do what some cruise missiles do, look at the ground below and find the most similar image in a big database of aerial photographs. The insane thing about this approach is that it was done in the 50s![0]

Another approach would be to do what insects do and use optical flow. Essentially look at how fast the ground is moving to figure how fast the UAS is moving and integrate to figure out where you are. This is exactly how optical mice work, in fact optical mice sensors have even been used to do this. Below is an example of a quadcopter that employs such system.[2]

[0] https://en.wikipedia.org/wiki/TERCOM [1] https://en.wikipedia.org/wiki/Optical_flow [2] https://www.youtube.com/watch?v=bbS1N--bT0w

The difference here is that a drone will not be doing 2200mph over 3k miles so differences in the position of stars won't be particularly noticeable. You may be able to do some trickery with a few outward facing cameras and some software to map the horizon though.

Yeah, I'd trust it more as a source of direction than a magnetometer though.

Horizon tracking would be super cool. You'd have to open your cameras to blinding attacks again to make that work, but still. Even as a project unrelated to getting around jamming, that would be a neat piece of tech.

People have done just that using the Xbox Kinect. https://www.youtube.com/watch?v=kmMzc2-ray0

If I really wanted to get around this, you can just use your magnetometer and do a 180 whenever you get interference. Combined with a pressure sensor (typically accurate to within a few feet of altitude if calibrated correctly) you can probably escape without issue. If you really wanted to be a PITA, just pick an arbitrary frequency pair and let https://en.wikipedia.org/wiki/Instrument_landing_system be your guide.

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