Re: Face-Recognition Technology Improves

[Bill Stewart]

At 09:01 AM 03/15/2003 -0500, Derek Atkins wrote:
"Sidney Markowitz" <[EMAIL PROTECTED]> writes:

> > In addition, only one subject in 100 is falsely linked
> > to an image in the data base in the top systems.
>
> Wow, 99% accuracy for false positives! That means only a little more than
> 750000 people a year mistakenly detained for questioning in Atlanta
> HartsField Airport (ATL), and even fewer at the less busy airports (source
> Airports Council International, 10 Busiest Airports in US by Number of
> Passengers, 2001).
Were there really 750 Million Passengers flying through ATL???  That
number seems a bit high...
750,000 * 100 = 75,000,000 usually (:-), which sounds more credible.
No idea how many of those are unique passengers, but there are probably
a lot of frequent business travellers going through there many times.
Also, I'm not convinced that multiple trials for a single individual
are independent.  Indeed, one could easily assume that multiple trials
for a single individual are highly correlated -- if the machine isn't
going to recognize the person on the first try it's highly unliklely
it will recognize the person on subsequent tries.  It's not like there
is a positive feedback mechanism.
They're probably not independent, but they'll be influenced by lighting,
precise viewing angles, etc., so they're probably nowhere near 100% 
correlated either.
There could be some positive feedback, if they keep photographs of near 
matches.
Another mechanism they could use is the set of names of people expected
to fly in and out of the airport, but of course that only works for people
who use their real names on airline tickets - it's better for tracking
Green Party members than for tracking Carlos the Jackal.

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