Marker set information

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1

Dear Sir/Madam
I am trying to do inverse dynamic analysis by using GaitLowerExtremity and GaitFullBody.
I suppose some of markers’ position using by Anybody model are different from our ones although those have same name. In example, the markers such as RANK/LANK are clear but the exact position of RTHI/LTHI, T10, STRN etc may different from researchers.

May I ask additional information about your marker set in detail? then it will help me to decide offset values of them.

Thank you
Seungkook Jun

2

Dear Seungkook Jun,

  1. If you see the ‘ModelSetup.any’ file then you can find the definition of RTHI marker:
CreateMarkerTD RTHI ( 
  MarkerName=PrefixDef(RTHI),
  MarkerPlacement =Right.Leg.Seg.Thigh, 
  OptX="[b]On[/b]",OptY="[b]On[/b]",OptZ="[b]On[/b]",
  WeightX=1.0,WeightY=1.0,WeightZ=1.0,
  
  Model1=MotionAndParameterOptimizationModel, Model2= InverseDynamicModel
  )= {
    sRelOpt = {-0.03102465, -0.2669603, 0.1139464};
  };

This means that the coordinates (x, y, z ) of RTHI marker will be optimized during the MotionAndParameterOptimizationModel process.

  1. If you see the ‘GaitNormal0001-processed-OptimizedParameters.txt’ file in the GaitFullBody example, then you can find these 3 lines:
RTHIX 5.244726682114895e-002
RTHIY -1.568684190807868e-001
RTHIZ 9.103474528740208e-002

These are optimized coordinates of RTHI marker inside the thigh segment.
It means that even if you could not find a good initial guess of those values, AnyBody will optimize the marker locations as possible as it can.

  1. As you pointed out, there may not be a clear way to determine the very good initial guess of some marker locations such as RTHI and LTHI.
    The only way is to modify the sRelOpt values of those markers based on your eyesight.

Best regards,
Moonki