A system, comprising: a probe, comprising a tubular distal end section configured to be inserted into a cavity of a patient, wherein the distal end section comprises: a visually guiding object (32, 48) disposed over a perimeter of a distal edge of the distal end section; and a magnetic field sensor comprising two sensor coils (34a, 34b) aligned non-parallel with each other, the magnetic field sensor attached to the distal end section, and having: a first axis of symmetry, of one of the coils, which is aligned perpendicular to a central longitudinal axis of the distal end section; and a second axis of symmetry, of the remaining coil, which is aligned perpendicular to the central longitudinal axis of the distal end section and not parallel to the first axis of symmetry; and a processor of a magnetic tracking system, which is configured to: using signals received from the magnetic field sensor coils, calculate a position, direction and rotational orientation of the distal end section in the cavity of the patient; and register the measured position with a medical image; characterised in that the processor is further configured to: using the calculated direction and rotational orientation, find in the medical image: a first anatomical surface location along the direction of the central longitudinal axis; and a second anatomical surface location along a direction from the calculated position through the visually guiding object; and toggle a cursor between the first and second anatomical surface locations on the medical image on a display. a probe, comprising a tubular distal end section configured to be inserted into a cavity of a patient, wherein the distal end section comprises: a visually guiding object (32, 48) disposed over a perimeter of a distal edge of the distal end section; and a magnetic field sensor comprising two sensor coils (34a, 34b) aligned non-parallel with each other, the magnetic field sensor attached to the distal end section, and having: a first axis of symmetry, of one of the coils, which is aligned perpendicular to a central longitudinal axis of the distal end section; and a second axis of symmetry, of the remaining coil, which is aligned perpendicular to the central longitudinal axis of the distal end section and not parallel to the first axis of symmetry; and a first axis of symmetry, of one of the coils, which is aligned perpendicular to a central longitudinal axis of the distal end section; and a second axis of symmetry, of the remaining coil, which is aligned perpendicular to the central longitudinal axis of the distal end section and not parallel to the first axis of symmetry; and a processor of a magnetic tracking system, which is configured to: using signals received from the magnetic field sensor coils, calculate a position, direction and rotational orientation of the distal end section in the cavity of the patient; and register the measured position with a medical image; using signals received from the magnetic field sensor coils, calculate a position, direction and rotational orientation of the distal end section in the cavity of the patient; and register the measured position with a medical image; characterised in that the processor is further configured to: using the calculated direction and rotational orientation, find in the medical image: a first anatomical surface location along the direction of the central longitudinal axis; and a second anatomical surface location along a direction from the calculated position through the visually guiding object; and toggle a cursor between the first and second anatomical surface locations on the medical image on a display. using the calculated direction and rotational orientation, find in the medical image: a first anatomical surface location along the direction of the central longitudinal axis; and a second anatomical surface location along a direction from the calculated position through the visually guiding object; and a first anatomical surface location along the direction of the central longitudinal axis; and a second anatomical surface location along a direction from the calculated position through the visually guiding object; and toggle a cursor between the first and second anatomical surface locations on the medical image on a display.