Re: No matter where you go, there they are.

[rick hoselton <hoz@univel.telescan.com>]

At 10:04 AM 4/10/96 -0400, Peter Wayner wrote:
>
>Hmm. Here's an interesting question.  Let's say that there are 3
>satellites in view broadcasting signals f1(t), f2(t) and f3(t).
>...Okay, so why can't I just tape the signals I get from each of
>the three satellites. 

>Or course, I could be completely missing some neat feature of
>DGPS. ... Any thoughts?

I have read that GPS uses encryption to place time-dependent, 
location-dependent inaccuracies into the signals.  Innacuracies 
small enough so they are not a problem for civilian navigation, 
(mostly) but large enough to prevent GPS from being a useful method 
of military targeting for anyone who does not hold the keys.

Perhaps Ms. Denning is suggesting that the US feral government could 
act as a "trusted server" (and she has repeatedly suggested such trust) 
and tell us whether a GPS that "thinks" it's at some location, right now, 
is REALLY at some known location.