IV. Curvature Estimation
Another aspect of the sequence z0, z1, z2… zn that can be measured is the curvature between consecutive iterations. A quick estimate can be obtained by using only the last two orbit points. A more thorough measure can be obtained by averaging  over all iterations.
A variation on this method determines the radius of a circle passing through three consecutive orbit points. This factors in not only the angle between consecutive points, but the distance between them as well.