Abstract: A marker for remote localisation in a medium, the marker including a magnetic field sensor configured to measure three different magnetic fields at three different respective times in three dimensions at a marker location in the medium, wherein the marker is configured to generate measurement data representing the measured magnetic fields for determining the marker location.

Abstract: A marker for remote localisation in a medium, the marker including a magnetic field sensor configured to measure three different magnetic fields at three different respective times in three dimensions at a marker location in the medium, wherein the marker is configured to generate measurement data representing the measured magnetic fields for determining the marker location.

Abstract: Method and system for detecting magnetic contaminants in products (160). The product (160) is transported past magnetic sensors (170, 180) which return a first sensed signal S1 (172) and a second sensed signal S2 (182) being time-spaced received versions of the source signal produced by the product (160). From the sensed signals (172, 182) it is determined whether a magnetic contaminant has been detected. Gradiometry may be applied between the signals (172, 182). A so-called auto-cross-correlation comprising +/?(CC1+CC2?AC1?AC2) derived from the cross-correlation (CC1) of S1 with S2, the cross-correlation (CC2) of S2 with S1, the autocorrelation (AC1) of S1 and the autocorrelation (AC2) of S2, may be used to improve signal recovery from noise. The auto-cross-correlation may be applied in other applications.