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["Don Bowen" <don.bowen AT earthlink.net>]

> I don't unterstand a lot of this
> new technology, but the other article maintained that it could track you
> anwaywhere you walked by an rfid screener (passive, like you said), just
> like cell phones can be traced today from their pings

An RFID tag on your credit card would allow you to be tracked anywhere there
is a scanner.  Big chain stores really want to know your path through the
store and what you are buying.  That way they can place stuff for you walk
by.  It is no accident that the meat and milk are at the back of the store.

A cell phone on the other hand can be traced in a couple of ways.  The much
less accurate method is by cells.  Look at the tower and you see three
antennas arranged in groups of three.  That gives three cells and the
network knows which one you are in and when you cross boundaries.  Seamless
handoff is tricky.  But it is not all that accurate, they only know about
where you are.

If the cell phone can receive and decode GPS signals then encode that into a
Short Message Service then they can know where you are within just a few
feet.  They the whole idea sold on the basis of 911 calls but it is also
used to track and now as an added extra charge service help you find the
nearest gas station of restaurant, of course the gas station or restaurant
has also paid to be listed.  It does not work well in buildings because the
GPS signal is too weak.

Don Bowen  KI6DIU
http://www.braingarage.com/Dons/Travels/journal/Journal.html