An orientation determination device comprising: - data input circuitry configured to obtain magnetic field sensor data comprising at least two magnetic field measurements sensed by one or more magnetic field sensors (20a, 20b) at spatially separate positions and/or in separate frequency ranges and/or at different times and/or at different codes, - position input circuitry configured to obtain a position estimate of the one or more positions of the one or more magnetic field sensors at which the magnetic field sensor data have been acquired, and - estimation circuitry configured to derive, from a magnetic map, azimuth and inclination data at the one or more positions of the one or more magnetic field sensors indicated by the obtained position estimate and to estimate the orientation of the orientation determination device based on the obtained magnetic field sensor data and the azimuth and inclination data derived from the magnetic map, wherein said data input circuitry is configured to obtain magnetic field sensor data comprising i) magnetic field measurements sensed by a single magnetic field sensor at different time instances and at spatially separate positions, wherein the orientation of the single magnetic field sensor at said spatially separate positions is fixed or tracked by an orientation sensor forming a common sensor unit together with the magnetic field sensor or ii) magnetic field measurements sensed by a single magnetic field sensor in separate frequency ranges and/or at different times and/or at different codes, wherein one of said magnetic field measurements represents a magnetic beacon signal in a frequency range used by one or more magnetic beacons and/or emitted at a time used by one or more magnetic beacons and/or with a code used by one or more magnetic beacons. - data input circuitry configured to obtain magnetic field sensor data comprising at least two magnetic field measurements sensed by one or more magnetic field sensors (20a, 20b) at spatially separate positions and/or in separate frequency ranges and/or at different times and/or at different codes, - position input circuitry configured to obtain a position estimate of the one or more positions of the one or more magnetic field sensors at which the magnetic field sensor data have been acquired, and - estimation circuitry configured to derive, from a magnetic map, azimuth and inclination data at the one or more positions of the one or more magnetic field sensors indicated by the obtained position estimate and to estimate the orientation of the orientation determination device based on the obtained magnetic field sensor data and the azimuth and inclination data derived from the magnetic map, i) magnetic field measurements sensed by a single magnetic field sensor at different time instances and at spatially separate positions, wherein the orientation of the single magnetic field sensor at said spatially separate positions is fixed or tracked by an orientation sensor forming a common sensor unit together with the magnetic field sensor or ii) magnetic field measurements sensed by a single magnetic field sensor in separate frequency ranges and/or at different times and/or at different codes, wherein one of said magnetic field measurements represents a magnetic beacon signal in a frequency range used by one or more magnetic beacons and/or emitted at a time used by one or more magnetic beacons and/or with a code used by one or more magnetic beacons.