Shadow Analysis Could Spot Terrorists

Hugh Pickens writes "An engineer at Jet Propulsion Labs says it should be possible to identify people from the way they walk — a technique called gait analysis, whose power lies in the fact that a person's walking style is very hard to disguise. Adrian Stoica has written software that recognizes human movement in aerial and satellite video footage by isolating moving shadows and using data on the time of day and the camera angle to correct shadows that are elongated or foreshortened. In tests on footage shot from the sixth floor of a building, Stoica says his software was indeed able to extract useful gait data. Extending the idea to satellites could prove trickier, though. Space imaging expert Bhupendra Jasani at King's College London says geostationary satellites simply don't have the resolution to provide useful detail. 'I find it hard to believe they could apply this technique from space,' says Jasani." Comments on the article speculate on the maximum resolution possible from KH-11 and KH-12 spy satellites.

Comments

Upon deployment....

[BitterOldGUy]

the terrorists start taking dance, yoga, and other lessons to change their walking style.

Go ahead, develop more technology, there's always around it.

Defeated

[Merls the Sneaky]

Defeated by a simple 2 inch lift in one shoe.

Wonderful euphemism

[Anonymous Coward]

I like how yet again ``spotting terrorists'' is an euphemism for ``spotting everyone else, too''. I habitually substitute ``spotting YOU'' and honestly think of all the good it would do.

Yes, there's useful stuff in there, but again only if those watching you can be trusted. This has been said often enough before and still people score cheap headlines with the same fallacy.

Anybody spot the shadow of a flying pig yet?

Solution in search of problem

[c]

So... um, you've got a "terrorist" under tight enough surveillance that you can build a "gait profile", but you're not arresting or just outright executing them?

Admittedly, I support this effort. Once complete, the DHS can take its rightful place as the Ministry of Funny Names and Walks.

c.

Bullshit and strawmen?

[Moraelin]

Bullshit and strawmen, whether intentional or not. The objections to false positives have more to do with statistics, than with slippery slopes or anything else.

E.g., let's say I have a system which can look at photos from the security cameras, and tell you if a face or gait in the crowd matches a terrorist profile with 99% accuracy. (Which is actually a lot higher than what most of these snake oil systems get.) The problem in that case isn't that it lets 1% of the terrorists go. It's that it also creates 1% false positives out of people who aren't, for just one terrorist's photo. Apply that to just one airport, say the JFK, with its almost 60,000 passengers per day. If you get exactly one photo of each passenger, that's 600 false positives per day, in just one airport, for just one terrorist. But more likely you'll have everyone caught by several cameras during their trip to the airport, so the number multiplies accordingly.

Now feed it a database of several tens of thousands of known criminals, suspects, etc, and watch the number of false positives explode. Given that accuracy, just 100 photos are enough to match a majority of the passengers at one point or another.

At some point you can simply swamp the security with false positives, to the point where it's worse than useless.

And it's not just a hypothetical scenario, it's what airport security people themselves have said about previous trials with face recognition system. That they're crap and worse than useless. Would you accuse those too of being paranoid and slippery-slope types, or just accept that they probably know their job enough to know when a gizmo isn't helping it?

So basically spare me the bullshit about "nirvana fallacies" and "paranoid liberals". Learn what the real problem is, before talking out the arse about.