An apparatus for generating a magnetic field for tracking of an object located in an area of interest, comprising the following: a localized magnetic field generator that is configured to generate a magnetic field and to control the magnetic field in the area of interest and configured to control the magnetic field in a separate area, wherein the separate area is displaced from the area of interest, and a magnetic field-disrupting component disposed in the separate area, wherein the localized magnetic field generator is a mobile localized magnetic field generator configured to be placed on a patient, and wherein the localized magnetic field generator is a hand-held device that can be placed proximate to a heart of the patient and comprises a magnetic field shield comprising a first side and a second side; and a plurality of magnetic transmitting elements (138 1, 138 2, 138 3) located proximate to the magnetic field shield and on the first side of the magnetic field shield, characterised in that the magnetic field shield includes a lip formed around a perimeter of the magnetic field shield; and the lip is formed on a same side of the magnetic field shield as the plurality of magnetic transmitting elements (138 1, 138 2, 138 3) are located. a localized magnetic field generator that is configured to generate a magnetic field and to control the magnetic field in the area of interest and configured to control the magnetic field in a separate area, wherein the separate area is displaced from the area of interest, and a magnetic field-disrupting component disposed in the separate area, wherein the localized magnetic field generator is a mobile localized magnetic field generator configured to be placed on a patient, and wherein the localized magnetic field generator is a hand-held device that can be placed proximate to a heart of the patient and comprises a magnetic field shield comprising a first side and a second side; and a plurality of magnetic transmitting elements (138 1, 138 2, 138 3) located proximate to the magnetic field shield and on the first side of the magnetic field shield, characterised in that the magnetic field shield includes a lip formed around a perimeter of the magnetic field shield; and the lip is formed on a same side of the magnetic field shield as the plurality of magnetic transmitting elements (138 1, 138 2, 138 3) are located. wherein the localized magnetic field generator is a mobile localized magnetic field generator configured to be placed on a patient, and wherein the localized magnetic field generator is a hand-held device that can be placed proximate to a heart of the patient and comprises a magnetic field shield comprising a first side and a second side; and a plurality of magnetic transmitting elements (138 1, 138 2, 138 3) located proximate to the magnetic field shield and on the first side of the magnetic field shield, characterised in that the magnetic field shield includes a lip formed around a perimeter of the magnetic field shield; and the lip is formed on a same side of the magnetic field shield as the plurality of magnetic transmitting elements (138 1, 138 2, 138 3) are located. a magnetic field shield comprising a first side and a second side; and a plurality of magnetic transmitting elements (138 1, 138 2, 138 3) located proximate to the magnetic field shield and on the first side of the magnetic field shield, characterised in that the magnetic field shield includes a lip formed around a perimeter of the magnetic field shield; and the lip is formed on a same side of the magnetic field shield as the plurality of magnetic transmitting elements (138 1, 138 2, 138 3) are located.