A method for determining the 3D location of a catheter distal end portion in a patient's body, the distal end portion including an electrode, the method comprising: (a) placing first and second body-surface patches on the patient in positions such that body region of interest is therebetween； (b) driving an alternating current between the patches； (c) measuring the voltage at the electrode and substantially contemporaneously capturing a 2D fluoroscopic image of the region of interest； and (d) determining the 3D location of the catheter distal end portion from the image and the measured voltage. A primary application of this method is 3D navigation during cardiac interventional procedures.
