An apparatus for distant detection of ferrous metallic objects includes a plurality of magnetic field sensors and a fingerprint processing system. The plurality of magnetic field sensors each measure an ambient magnetic field. The fingerprint processing system receives, from the plurality of magnetic field sensors, magnetic field data corresponding to the ambient magnetic field. The fingerprint processing system also generates, from the magnetic field data, a magnetic fingerprint image of one or more perturbations of the ambient magnetic field. The plurality of magnetic field sensors is separated from the ferrous metallic objects being detected by a detection distance that is greater than or equal to 0.5 meters.