[Razor]

The intentionally added 'error' to the GPS signal is called Selective Availability. Its not actually a 'crypto' signal; it was a deliberate offset added to the C(A) (uncoded civilian) signal. It was not added to the P(Y) (coded government) signal, thereby allowing someone with a P(Y) enabled receiver to get SA-free data. SA was removed from day-to-day use by order of then-President Clinton. Actually, this was not a bad move, considering the sheer number of civilians using it, from commercial airlines to search-and-rescue units to ships asea.

This does not, however, mean that the need for a COMSEC-keyed PLGR has vanished. The encrypted P(Y) code that only a keyed receiver can pick up provides protection against spoofing, and even a degree of protection against jamming (versus both an unkeyed military receiver and a civilian receiver). Although there has been no observed threat spoofing signals to date, the Iraqis did employ jamming equipment during OIF I, so the threat does exist.

Later this FY, units will begin receiving the Defense Advanced GPS Receiver (DAGR). This PLGR replacement weighs half as much, and is 2/3 the size of the current PLGR. Increased capability comes in the form of reduced time to first fix, the ability to receive two encoded signals at once (which greatly increases accuracy through better ionosopheric interference reduction), easier key/rekey procedures, and the inclusion of the Selective Availability/Anti-Spoofing Module, which greatly increases the anti-spoof/anti-jam capabilities of the receiver, and also increases the security of the coded signals. So, very shortly the advantage of using small, commercial GPS receivers may not outweigh the enhanced performance of a government receiver.