Oh, and I think what ShadowTail meant was to have circles in at least two, better three coordinate planes, not just in one.
E.g. if you scan a thin round pebble, dont just lay it on its flat side and then turn it upside down (180°), which would be most obvious and convenient. Also do one circle with it standing on the edge (you can use some modeling clay for that), ideally another one with it rotated 90° along the edge.
Forgive me if I am carrying owls to athens with that…