(a) Example of an SDN image in which shadows caused by the convex shape of the smooth patch are visible. The red lines are aligned with the direction of the Sun and were used to measure the length of the shadows. (b) Example of an ITS image showing the edges of the large smooth patch as seen from the camera. The red circles represent multiple measurements taken along the entire edge. In both figures, the white arrows indicate the meridian (see Figure 2 for reference).