this invention is an invasive probe apparatus including flexible elongate probe having a distal portion adjacent to a distal end thereof for insertion into the body of a subject , which portion assumes a predetermined curve form when a force is applied thereto . first and second sensors are fixed to the distal portion of the probe in known positions relative to the distal end , which sensors generate signals responsive to bending of the probe . signal processing circuitry receives the bend responsive signals and processes them to find position and orientation coordinates of at least the first sensor , and to determine the locations of a plurality of points along the length of the distal portion of the probe .