If you accept the premise that if the Impact Plane Line and Low Point Plane line are one of the same when the ball is located at low point, then you have two variables to identify.
1. Ball location with respect to the Low Point
2. Angle of the Inclined Plane
Sounds simple but when a golfer located the ball back further other adjustment are made to accomodate the ball position so that the height of the ball does not have to be increased. Think about it, if you play the ball off you rear foot with a wedge and your normal divot is say 4 inches long, moving the ball back that far without any other changes would make for a very long and very deep divot.
Matt had a diagram which showed the lines rather well.
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