For an observer equipped with a first azimuth data source responsive to a magnetic field to deliver first azimuth data, such as a compass, and with a second azimuth data source delivering second azimuth data and which is independent of magnetic fields, such as a gyroscope. The azimuth is determined by: analyzing the first and second azimuth data to determine whether a magnetic disturbance is present, and determining azimuth selectively on the basis of: the first azimuth data, the second azimuth data, or a combination of the first and second azimuth data, as a function of the result of the comparing step. In an embodiment, the choices of azimuth data source and events such as magnetic disturbances, sensor updates, types of trajectory deduced, are stored as a history sequence over successive time windows, by analogy with a DNA sequence, and is exploited for optimizing azimuth or navigation results.