Abstract: This invention is an invasive probe apparatus including flexible elongate probe (20) having a distal portion adjacent to a distal end (22) 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 (28, 30) are fixed to the distal portion of the probe (20) in known positions relative to the distal end (22), which sensors generate signals responsive to bending of the probe. Signal processing circuitry (36) receives the bend responsive signals and processes them to find position and orientation coordinates of at least the first sensor (28), and to determine the locations of a plurality of points along the length of the distal portion of the probe.