Final: angular redundancy

1. Has to be done.
2. cannot be perfectly done.
3. hard sampling is still by far the best method, as opposed to radius-line-distance based free clustering.
4. usually there shouldn't be any missed out points, if we select the entired region bounded by the rough diff(va_edge) detection.
   
5. some missed out points have to be fixed during the next step: sting removal based on w/z.