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. <EOS>