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Best-fit Alignments: Least squares vs. Vector

Which is the better Best-Fit alignment to use when comparing point deviation to CAD models? (Least Squares or Vector) Example, I am measuring these 36 points and using a 3D best-fit alignment. I am getting pretty substantial differences in the profile depending on the best-fit type. I have Rotate and Translate 3D alignment, but in the Least-SQR alignment it appears a -X- translation would help. What am I doing wrong?

RECALL/ALIGNMENT,INTERNAL,A5
A8 =ALIGNMENT/START,RECALL:A5,LIST=YES
ALIGNMENT/BF3D,LEAST_SQR,CREATE WEIGHTS=NO,ROTANDTRANS,USE SCALING=NO,-0.0053,0,-0.0032,-0.0004,-0.001,-0.0102
ITERATEANDREPIERCECAD=NO
Deviation Threshold=0.0003937
SHOWALLINPUTS=NO,SHOWALLPARAMS=NO
ALIGNMENT/END
FORMAT/TEXT,OPTIONS, ,HEADINGS,SYMBOLS, ;NOM,MAXMIN, , , , ,
SCN1 =FEAT/SET,CARTESIAN
THEO/<0,-1,0>,<0,1,0>
ACTL/<0,-1,0>,<0,1,0>
CONSTR/SET,BASIC,PNT145,PNT146,PNT147,PNT148,PNT149,PNT150,PNT151,PNT152,PNT153,PNT154,PNT155,PNT156,PNT157 ,PNT158,PNT159,PNT160,PNT161,PNT162,PNT163,PNT164, PNT165,PNT166,PNT167,PNT168,PNT169,PNT170,PNT171,PNT172,PNT173,PNT174,PNT175,$
PNT176,PNT177,PNT178,PNT179,PNT180,,
DIM PROF5= PROFILE OF SURFACE OF SET SCN1 FORMANDLOCATION UNITS=MM ,$
GRAPH=ON TEXT=OFF MULT=100.00 ARROWDENSITY=100 OUTPUT=BOTH
AX NOMINAL MAX MIN
M 0.0000 0.1668 -0.1632 <---|--->



RECALL/ALIGNMENT,INTERNAL,A5
A8 =ALIGNMENT/START,RECALL:A5,LIST=YES
ALIGNMENT/BF3D,VECTOR_LST_SQR,CREATE WEIGHTS=NO,ROTANDTRANS,-0.0107,0,-0.0063,0.0059,-0.0011,-0.01
ITERATEANDREPIERCECAD=NO
Deviation Threshold=0.0003937
SHOWALLINPUTS=NO,SHOWALLPARAMS=NO
ALIGNMENT/END
FORMAT/TEXT,OPTIONS, ,HEADINGS,SYMBOLS, ;NOM,MAXMIN, , , , ,
SCN1 =FEAT/SET,CARTESIAN
THEO/<0,-1,0>,<0,1,0>
ACTL/<0.0053,-1,0.0031>,<0.0001093,1,0.0000014>
CONSTR/SET,BASIC,PNT145,PNT146,PNT147,PNT148,PNT149,PNT150,PNT151,PNT152,PNT153,PNT154,PNT155,PNT156,PNT157 ,PNT158,PNT159,PNT160,PNT161,PNT162,PNT163,PNT164, PNT165,PNT166,PNT167,PNT168,PNT169,PNT170,PNT171,PNT172,PNT173,PNT174,PNT175,$
PNT176,PNT177,PNT178,PNT179,PNT180,,
DIM PROF5= PROFILE OF SURFACE OF SET SCN1 FORMANDLOCATION UNITS=MM ,$
GRAPH=ON TEXT=OFF MULT=100.00 ARROWDENSITY=100 OUTPUT=BOTH
AX NOMINAL MAX MIN
M 0.0000 0.0304 -0.0151 ----|#---
Parents
  • : here you are !
    For those who would use it, there's an explanation of how to install solver.
    You just have to change columns for theo values XYZ IJK and measured values, please don't change others columns.
    The actual sheet is setted as columns as letters and row as numbers, so "macro" works like this.
    Actual values are also setted to calculate 6 DoF, which is not a good idea for a cone (actual theo and meas values).
    You just have to change " ByChange:="$M$3:$M$8" " by ByChange:="$M$3:$M$7" if you want to avoid Z rotation.

    Enjoy with it, or tear your hair out, I don't know exactly how it could work in another language and another Excel settings Disappointed.

    It's friday, have a nice week-end, all !

    BF solver.zip
Reply
  • : here you are !
    For those who would use it, there's an explanation of how to install solver.
    You just have to change columns for theo values XYZ IJK and measured values, please don't change others columns.
    The actual sheet is setted as columns as letters and row as numbers, so "macro" works like this.
    Actual values are also setted to calculate 6 DoF, which is not a good idea for a cone (actual theo and meas values).
    You just have to change " ByChange:="$M$3:$M$8" " by ByChange:="$M$3:$M$7" if you want to avoid Z rotation.

    Enjoy with it, or tear your hair out, I don't know exactly how it could work in another language and another Excel settings Disappointed.

    It's friday, have a nice week-end, all !

    BF solver.zip
Children
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