Patent ID: 7421340

Claim:
A method of determining an azimuth using a first azimuth data source responsive to a magnetic field to deliver first azimuth data, and a second azimuth data source delivering, independent of magnetic field, second azimuth data comprising the steps of: analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and determining said azimuth selectively on the basis of: said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data, based on the determination of said analyzing step, wherein said analyzing step comprises the sub-steps of: acquiring said first and second azimuth data over a plurality of sampling periods within a time window, performing a statistical analysis on said first and second azimuth data for said sampling periods, and identifying a magnetic field disturbance on the basis of said statistical analysis, and wherein said azimuth determining step comprises basing the determined azimuth, in a situation in which a magnetic disturbance is determined to be present, on one of: i) said second azimuth data without reference to the first azimuth data, or ii) a combination of said second azimuth data and said first azimuth data.