scaling issue

[abeer mohamed]

Hi all
I applied 3DgaitModel2354, on the scaling tool page, I loaded Subject01_Setup_scale.xml file. I replaced the
static trc files in the scale model and adjust model markers sections by my subject static trc files, also type
my subject mass on the mass section.I uncheck the markers highlighted in red under the 'static pose weights' and run
it. the scale was able to run, however the scaling model looks strange specially the pelvis posture, top head and
sternum markers are missing. I adjustec the marker weight and scale factor, now, I'm able to see both sternum and top head marker, also the pelvis posture seem much better, however I'm still getting the high error as folow;
in the scripting shell window shows very large error;
"fram at (t=0): total squared error=0.281234, marker
errror: RMS=0.0896395, max=0.200271(L.Shank.Front)".
any suggestions
thanks
abeer

[Dustin Crouch]

Hello Abeer,

When the scaling tool adjusts the model markers, it may move the markers inside the segments, depending on the relative tracking weights among markers. That may be why adjusting the marker weights made the previously hidden markers appear in later runs with the scaling tool.

Your max error of 20 cm at the shank is a lot, and may be due to several factors. Check that the weights of other markers is not too high - this may cause the shank virtual marker to not track well with the experimental data. Check whether your virtual markers are placed appropriately relative to body segments before scaling. Finally, make sure the markers you use to scale the segments are along the same direction that the segment is scaled. You can read about all of this in the user's guide. You may have to iteratively adjust the marker weights several times until you are satisfied with the final marker adjustments.

Hope this helps.
Dustin