- Fully constrained alignment
- Two holes located in a plane in X
- The plane is the datum for a TP for these two holes
- GeoTol calculates the TP according to the hole positions in the alignment, but displays the coords as if in GeoTols datum alignment?
From what I can gather, the actual distance between the measured features are 29.985 between each other, which if GeoTol calculated this
correctly would be in tolerance.
...and if you add the MEASURED values together, you will get 30 mm exactly, which in theory is possible. Now, if we only had something that showed us what happened with the datum shift...
I'm saying that GeoTol is wrong in this case and the TP is within tolerance.
Actually, I see from the location dimensions they're both approx 2mm lower than nominal. GeometricTols has shifted them around 1mm up.
I'm hazarding a guess it's doing a LeastSq best fit on them (because of the maths you can get the same number from a situation where you have a one positive and one negative deviation, as if you have two deviations in the same direction) - it's why we have a Vector Least Sq algorithm in the Best Fit alignments.
Out of interest, if you did a Least Sq best fit alignment on the two holes (2D Rotate and Translate in the X workplane) and then output the Location again do you see around a 1mm deviation after the best fit?