Re: Real-time surveillance of the police

[tcmay@netcom.com (Timothy C. May)]

Robert Hettinga wrote:

(quoting me)

> >On the topic of how these localizers actually work, I'm not at liberty
> >to talk about the technology. It's novel, and uses a *lot* if digital
> >signal processing. It doesn't use GPS and it's not a variant of
> >cellular telephones.
> 
> I wonder if they're using an active/transponder system. That's what
> O'Niell's Geostar system was designed with in the early '80's. It would
> have put up cheaper sattellites and smaller earth transponders.  The way
> you saved on transponder size was with very small bursts at very high
> power. You could send a signal to a small net of satellites 30,000 miles up
> with a box initially no bigger than an HP12C, and which would shrink more
> with time.

I don't plan to say much more, and won't be playing the "Twenty
Questions" game, but the system does _not_ use satellites or anything
of that sort. Satellites up the ante considerably, and aren't even
needed.

Radio is enough to get 1% positional accuracy (or better) and radio
can have better coverage in many places that GPS-like systems can't reach.

> the backs of commerce. The only thing which saved GPS for mere mortals like
> us was the MIC's usual severe understimate of Grove's Law and the
                                                ^^^^^^^^^^^
> exponential cost effectiveness of integrated circuits over time.

A minor nit, but that's "Moore's Law," an empirical observation made
by Gordon Moore, a founder of Intel and current Chairman, that
integrated circuit capacities (roughly, number of transistors, bits,
gates) were quadrupling every two years or so.

Gordon had this posted outside his cubicle (the guy was worth $300
million then, and he worked in a Westinghouse-walled cubicle....I
thought that was carrying egalitarianism a bit far...he's now worth
$1.5 billion) and we all wondered when the trend chart would be
broken. So far, it's been pretty accurate.

But of course his trend chart ("Moore's Law," so dubbed by pundits
around 1970, when he first showed his chart) is a conflation of a huge
number of interesting trends in lithography, capital spending,
microprocessor consumption, etc.

> If my hunch is correct, with lots more local antennas, the power
> requirements of the tranceiver, and as a result, the tranceiver size, gets
> pretty small. Small enough to be worn on one's ankle.

The transceivers get real small for other reasons, not because of
satellites. Think about this: no reason to have satellites 100 miles
overhead if there are thousands or tens of thousands of cooperating
units nearby....

I won't say more for now about this, even though the patent filings
may be accessible, and the work has been described at "Hackers" and a
few other places (including Washington, at ARPA, who is also funding
them--gulp). 

--Tim May


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