> When it first became available, kit was 100m, and the military
> version that called in another satellite to get 1m, but I think
> they all do that now...

JT> Not quite. You're thinking of Selective Availability. It was a
JT> system that effectively scrambled the lower order accuracy of
JT> the signal to increase the error to 100m. They used a psudeo
JT> random encryption system that cycled every two days or so, so,
JT> if you averaged a stationary reading over that time period you
JT> would get the 15m accuracy they originally quote. Military
JT> equipment decrypts that, so they get the 15m accuracy.

 Ahh. God bless Amurrica and our masters the CIA.

JT> Selective Availability was turned off about May 2000? (can't
JT> remember exactly when) by the president at that time making
JT> available the full accuracy of the system to civilians.

 Either that, or they found a sneakier way to fuck it up.

 Do you know if there are other GPS systems up and running? The Japs
have launched heaps of satellites lately...

JT> Since then, they have introduced WAAS (Wide Area Augmentation
JT> Service) which is loosely based on DGPS (corrected GPS) but
JT> only works in the US. (And only will ever work in the US due to
JT> it's control system). 

 I am very suspicious of the USA, GPS and the Internet. I thought it
was very significant how *quickly* they caught this latest dork
spreading Miscrosoft virus. It was as if they went *straight* to him.

 I know they spread the story he was registering the computers
he infected, but durr... did anyone believe that?

 My guess is that the USA (probably NSA) has centralised the total
Net now.

Regards,
Bob


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