Illustration of rotation (left) and precession (right) geometries considered here. The left image is shown in the inertial coordinate system, which is fixed at the center of the neutron star. The right image is shown in the body fixed coordinate system. The X-axis is toward the right. The Z-axis is up. In case of rotation (left), the rotation axis is along Z-axis. In case of precession (right), the precession axis (symmetric axis) is along Z-axis. Motion is illustrated with large dashed line having arrows at regular intervals. The measured PA is appropriately marked.