> In GPS technology, the term "COCOM Limits" also refers to a limit placed on GPS tracking devices that disables tracking when the device calculates that it is moving faster than 1,000 knots (1,900 km/h; 1,200 mph) at an altitude higher than 18,000 m (59,000 ft).[2] This was intended to prevent the use of GPS in intercontinental ballistic missile-like applications.
/EDIT SEE BELOW
AFAIK star-based and inertial navigation.
For the shipping containers (not ballistic missiles) they'll most likely smuggling these in on, for the next few years, any COTS system (on an appropriately flagged freighter) will suffice to get them across the Pacific. From there they'll just usual visual identification to get it close enough to place it could do enough damage. Like near the Embarcadero, say.