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[tigers_gonads]

The James Bond film "Tomorrow never dies" was more true to life then alot of people realised 

Its also highly probable that the US reaper / preditor drone that has gone walk about reciently was probably spoofed 

[Kevin Wood]

Yep.. I worked on A-GPS in mobile phones a few years back. 

SA (as it's called) encrypts the least significant bits of the timing signal so, unless you have a key to decrypt this again, you get a small random error on the "time of flight" from each satellite to the receiver and hence on your position fix.

It became so easy to overcome using DGPS, where a ground station evaluates the error and retransmits to local receivers, that it became pretty pointless. Many networks use GPS as a precise time and frequency reference now, so turning it back on would pee them off a little, without achieving its' original aims. You can bet they have an alternative now, which would be switched on in times of conflict. They are not making the mistake of telling anyone how it works in advance, though!

IIRC, SA was turned off during gulf war 1 due to lack of availability of SA decoders, so troops were using commercial receivers instead. I know I did a trial of a mobile phone coverage mapping system around then, and was surprised how well the resultant plots overlaid onto an OS map. 

Getting a bit warm, so I'll take this anorak off.

[tigers_gonads]

Yep.. I worked on A-GPS in mobile phones a few years back. 

SA (as it's called) encrypts the least significant bits of the timing signal so, unless you have a key to decrypt this again, you get a small random error on the "time of flight" from each satellite to the receiver and hence on your position fix.

It became so easy to overcome using DGPS, where a ground station evaluates the error and retransmits to local receivers, that it became pretty pointless. Many networks use GPS as a precise time and frequency reference now, so turning it back on would pee them off a little, without achieving its' original aims. You can bet they have an alternative now, which would be switched on in times of conflict. They are not making the mistake of telling anyone how it works in advance, though!

IIRC, SA was turned off during gulf war 1 due to lack of availability of SA decoders, so troops were using commercial receivers instead. I know I did a trial of a mobile phone coverage mapping system around then, and was surprised how well the resultant plots overlaid onto an OS map. 

Getting a bit warm, so I'll take this anorak off.

Civvy incription iirc is accurate down to about 3 meters at best.
The stuff that the forces use is accurate in weapons form encription is good for less then a meter 
Infact, the yanks Jdam bombs are more accurate now then laser guided bombs were 20 years ago 

Best not say anymore or i'll have men in a black omega banging on my door