A catheter is navigated within a body cavity of a patient. This navigation is enabled by the provision of the transmitter of electromagnetic radiation under platform, a receiver of electromagnetic radiation rigidly attached to fluoroscope, and a receiver of radiation rigidly attached to the catheter, all three of which are connected by wires to a computer. The computer displays, on a display unit, the image of the body cavity acquired by the fluoroscope, with an icon representing the catheter superposed on the image in the location and orientation of catheter relative to the body. There is no representational imaging device equipped with a receiver in the apparatus of the current invention.