Cardiac catheterization is carried out by clothing a subject in a torso vest having a plurality of sensing electrodes, magnetic location sensors, active current location sensors and patches for establishing galvanic contact with the skin. A multi-electrode probe is inserted into a cardiac chamber such that a plurality of intracardiac electrodes are disposed at respective locations in the heart. Respective locations are determined using the active current location sensors, Electrical calibration signals are emitted from the intracardiac electrodes, and received in the sensing electrodes of the torso vest. Relationships between the emitted calibration signals and the received calibration signals in the intracardiac electrodes are established to map a correspondence between the received calibration signals and the respective locations.
