[Myrddin]

It seems we could shut down the civilian GPS network(which the Iraqis are surely using) in an emergency with relatively little impact on military operations.

You can't shutdown the "civilian GPS". That is what is known as the C/A channel. Part of the C/A channel information is a current "bookmark" for the pseudo random number sequence that is being broadcast on the encrypted channel. That PN sequence repeats every 7 days, so you need some way to latch onto the current spot. You also need the current crypto key to encrypt your version of the PN sequence to attempt to get "chip sync" with the encrypted channel.

[znix]

You can't shutdown the "civilian GPS".

Okay im following part of your explanation here. If the C/A channel is required to make use of the encypted channel then what can be done?