In an embodiment, a method comprises: obtaining, by a sensing device on a ferromagnetic surface, a first magnetometer reading of magnetic flux density modified by the ferromagnetic surface in a first direction; obtaining, by the sensing device, a second magnetometer reading of magnetic flux density modified by the ferromagnetic surface in a second direction; obtaining, by the sensing device, sensitivity terms based on the first and second magnetometer readings; and storing, by the sensing device, the sensitivity terms and a location of the sensing device on the ferromagnetic surface.