Patent ID: 8018708

Claim:
A method for magnetically compensating the magnetic field distortion occasioned by a ferromagnetic portion of the hull of a vessel: providing a plurality of electromagnets at a plurality of predetermined locations throughout said vessel, when energized, producing a directional magnetic field for compensating said magnetic field distortion; storing in a first memory, earth's magnetic field map, which is a database of information on the earth's magnetic field at potential vessel locations; obtaining the vessel's navigation information which includes the location of said vessel, and its heading, pitch and roll information; determining the likely magnetic field distortion outside the vessel using the earth's magnetic field map stored in said first memory and the vessel's navigation information; storing in a second memory, information on the location of said electromagnets within the vessel, the field intensity and the field direction of each of said electromagnets in response to said magnetic field distortion outside the vessel; determining, from said magnetic field distortion outside the vessel and said information stored in said second memory, a desired amount of direct current to be applied to each of said electromagnets for generating compensating magnetic fields having direction and magnitudes for canceling said magnetic field distortion outside the vessel; and energizing said electromagnets by applying to each of said electromagnets said desired amount of direct current, thereby creating a net magnetic field vector substantially equal and oppositely poled to said magnetic field distortion.