Method and system for determining the current position of a selected portion of a medical catheter inserted into a tubular organ of the body of a patient, the method comprising the procedures of inserting a medical positioning system (MPS) catheter into the tubular organ, acquiring a plurality of mapping positions within the tubular organ, displaying a mapping position representation of the mapping positions, constructing a mapping path according to the mapping positions, inserting the medical catheter into the tubular organ until the selected portion reaches the initial position, displaying an operational image of the tubular organ, a path representation of the mapping path, and an initial position representation of the initial position superimposed on the operational image, registering the selected portion with the initial position, measuring a traveled length of the medical catheter within the tubular organ from the initial position, and estimating the current position.
