Navigation method for vehicles with electronic compass

Claim 1

In a method for determining the direction of the earth magnetic field, the north direction and the travelling direction of a vehicle by means of a magnetometer fixedly mounted in said vehicle to measure components of a magnetic field effective at the magnetometer and by means of an evaluation circuit which cyclically evaluates and stores the measured components as electric measurement values defining parameters of an elliptical locus diagram of the magnetic field, inclusive of the magnitude and direction of hard-magnetic and soft-magnetic interfering fields, and calculates the direction of the earth magnetic field with respect to the travelling direction, an improvement comprising the steps of (a) cyclically determining a nominal vector (v B ) which on the elliptical locus diagram is associated with a vector (v M ) of the magnetic field effective at a magnetometer; (b) determining from the nominal vector (v B ), a current hard-magnetic interfering field vector (H H ) and the magnetic field vector (v M ) a resultant vector (v K ) which indicates a change of the hard-magnetic interfering field; (c) weighting the resultant vector (v K ) with a factor k<1, (d) adding the weighted resultant vector (k.v K ) to the current hard-magnetic interfering vector (H H ) to form a new hard-magnetic interfering field vector (H H ,), and (e) for dynamically compensating changes of the hard-magnetic interfering field, calculating the direction of the earth magnetic field with respect to the travelling direction by using the new hard-magnetic interfering field vector (H H ,) (f) selecting the factor k in dependence on the cycle time (T) of the measurement value acquisition, in such a manner that the interfering field changes (v K ) occurring for a short time over a few seconds are almost suppressed.