Calibration method and device for carrying it out

Electromagnetic tracking systems and methods for automatically providing the required additional information needed to identify the orientation of a sensor are disclosed. The tracking systems are configured to carry out a digital modulation process to determine one or more parameters needed for calibration and to determine if the carrier wave and the modulated signal are in-phase or 180° out-of-phase at time T=0, thereby determining the operational sign of the carrier wave and thus the orientation of the one or more sensors. In some embodiments, at least one offset coil is arranged to generate an additional magnetic field, and the tracking system may be calibrated on the basis of the additional magnetic field.