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Comment by yodon | Hacker News Reader

I made a couple trips to the South Pole in grad school. Down there you were either a scientist in a red parka, black insulated pants, and white boots or support staff in brown carharts. No part of the body could be seen at a distance and even the gloves were standard issue.

What constantly amazed me was how you could see someone walking a quarter mile away and instantly know exactly who it was.

The South Pole is a smaller population than China so I'd be worried about false positives (probably mostly within families as kids learn to stand and walk like their parents and have similar dimensions when fully grown) but I suspect it's actually a pretty robust identification technique.

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> The South Pole is a smaller population than China so I'd be worried about false positives

Even if the false positive rate is really low, it's still a problem. All of these dragnet-style things mess with your priors. In a traditional investigation, the police have a handful of suspects and then gather evidence. Circumstantial evidence showing that the chances are 1 in 1000 that this one of the five suspects was not the culprit is pretty convincing, and probably enough to convict.

Cast a dragnet over a city of 1 million, and suddenly that same 1-in-1000 error rate will be giving you 1000 innocent people who, under the old system, are 'guilty beyond reasonable doubt'. They've been pre-selected to look pretty frikkin' bad regardless of whether they're guilty, which means any one of them will have a hell of a time proving their innocence.

I suspect there’s quite a bit of case law on what probability of false positives is acceptable?

When I hear a roommate or family member walking down the stairs somewhere else in the house, I can immediately tell who it is based on the sound of the pattern of how fast and how hard they are walking.

Former Polie (10x; IceCube) - I also noticed this there. I wouldn't trust it 100%, but it was pretty reliable.

I expect that if you knew that the cameras were watching, you could trick their AI's pretty easily (e.g., by faking a limp), but I'd prefer to confirm that before relying on it :-).

Detecting an unnatural gait is probably a fairly easy AI task, unfortunately.

Kind of reminds me of Dunes "Walk without rhythm so you don't attract the worm"

Reminds me of Dune before Butler's Jihad.

Maybe. I think it's possible to develop a couple of different gaits, though it requires a lot of self-control to restrict specific gaits to specific situations.

I live in a block of flats with a flat mate. I can tell when she is home before she even gets to the front door as you can hear people walking in the corridor and she has a particularly heavy, almost clumsy walk that is completely and easily distinguishable.

I suspect that for humans, it’s actually not that difficult a feat.

Totally anecdotal, but I can often identify people I know just by listening to their footsteps.

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