Apparatus, including a magnetic tracking system, which generates a magnetic field near a living subject's body, and a probe, having a distal end that can contact registration points on a surface of the body. The probe has a contact sensor, located within the distal end, that outputs first signals indicative of a quality of the contact between the distal end with the registration points. Located within the distal end is a magnetic detector that outputs second signals that are indicative of respective positions of the registration points in a coordinate frame of the magnetic tracking system. A processor receives a tomographic image of the subject, and verifies, based on the quality of the contact indicated by the first signals, that the registration points are valid, and registers the tomographic image in the coordinate frame of the magnetic tracking system using the positions of the valid registration points.
