MITIGATING SYSTEMATIC ERROR IN GYROCOMPASSING

The present invention relates to a MEMS gyrocompass, a method performed by the MEMS gyrocompass and a computer program product. The MEMS gyrocompass mitigates systematic error in determination of a north angle. The MEMS gyrocompass comprises at least one MEMS gyroscope having a sense axis within a reference plane. Samples from an output of the at least one MEMS gyroscope are obtained in at least two angles of rotation about an axis perpendicular to the reference plane. First fit coefficients are determined by fitting samples obtained from each individual MEMS gyroscope with first fitting functions determined as function of time. Second fit coefficients are determined by fitting components of earth rotation rate projected on the reference plane based on samples obtained by all of the at least one MEMS gyroscope, which fitting is performed with a second fitting function determined as a function of rotation angle of the at least one MEMS gyroscope with respect to a reference angle. The north angle is determined as an angle between the reference angle and true north based on the second fit coefficients.