On Thu, 18 Dec 2003 21:40:13 -0500, "Ray Drouillard"
wrote:



Even if the non-encrypted civilian access GPS is turned off, the
military system will work fine.

Yes, another poster pointed that out, so I stand corrected. Also,
because the signals coming from the satellites are apparently spread
spectrum, it will be much less easy to reverse-engineer the codes than
I anticipated. Because we know what the output of the atomic clocks
should be, we know what the "clear" signal has to be. So I expected
extreme difficulties in encoding these signals - it's like trying to
design a good code when you have someone with access to the plaintext
working on breaking it.

However, with the spread spectrum approach, the difficulty will be to
be able to detect the signal in the broad-band noise.