Example of two free ellipse fits (cyan) applied to the same model disk, where edge points (red) were extracted at increasing azimuthal angles in one direction. Left: the detected edge points span 270° of a single side of the ring. Right: points span only 40° but are located on opposing sides of the ring. The two ellipses accurately map the underlying structure, showing the importance of extracting information from various azimuthal regions of the disk.