The geo positioning sats belong to the US. They were originally military only. Would our military planners have been so dumb as to not make them capable of encrypting the data in just such an event as this??
The NAVSTAR Global Positioning System indeed supports two codes: a civilian and an encrypted military. Initially, the system also featured
Selective Availability, which introduced random errors of up to 100 meter uncertainty to the civilian signal. However, Gulf War I placed such a demand on GPS devices, that the military was forced to use civilian devices and disabled Selective Availability.
Following pressure by the civilian sector (and the FAA), on May 1st, 1990 Clinton issed an executive order to set the Selective Availability error to 0 (essentially turning it off). From the point of view of civilian GPS industry, this isn't as bad as it sounds: we now depend on GPS in everything from fire fighting to emergency response to ship navigation.
The US military has since then developed methods of jamming GPS sattelites locally over an operational area, denying the enemy use of the system.
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