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.