Re: And the navigation systems for those Trident/Poseidon missiles?
No, the start point is a geographical reference point. OMEGA, GPS, and other data points are mapped against our INS which was a LASER Ring Gyro. In our case, since we (probably) carried Tomahawk Land Attack Missiles (TLAM), we had two of them. We trusted them a Hell of a lot more than SatNav or GPS.