There is a method of measuring small arcs from Hexagon floating around using Fixed rad and distance/polar to evaluate radius. The implementation I've seen consisted of measuring the arc with Fixed rad and evaluate the distance from the arc center to points on the radius.

I made this estimate of the result on an incorrect radius and had it verified in CMM:

rad.png

Nominal radius in green measured with 4 points. Red dashed the fixed radius. Blue actual radius. The distance from fixed radius center to a point in the middle of the radius

I made this estimate of the result on an incorrect radius and had it verified in CMM:

rad.png

Nominal radius in green measured with 4 points. Red dashed the fixed radius. Blue actual radius. The distance from fixed radius center to a point in the middle of the radius

**increases**when the actual radius is**smaller**. The distance to points on the edges will decrease slightly. The cooefficient of the function from the distance in between the points and the fixed radius center, to actual radius is nowhere near 1 in this implementation. I can't see any sustantial difference in any implementation I've seen. Am I missing something or is this method broken?
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