Perfecting Auto Labelling

There are a few ways to make your auto-labelling more reliable in Vicon Nexus 2. We will outline a few ways to perfect your process for auto-labelling.

Do your subject calibration

Our main piece of advice if you are struggling with the auto-labelling functions of Nexus is to ensure you have your subject fully calibrated. This can by done by running the “Auto initialize labeling” pipeline to scale and calibrate the marker layout for the specific subject for more robust labelling.

Alternatively ensure you run the following two operations as part of your subject calibration steps:

  1. Scale Subject
  2. Marker-only subject calibration

Offsetting your left and right markers

If you are still having issues with auto-labelling for plug-in-gait, particularly with Nexus discerning the left and right sides of the subject, make sure you have a height offsets/asymmetry between your mid segment markers. This asymmetry helps Nexus discern between the left and right segments when labelling.

The Vicon Nexus Documentation provided by Vicon provides the following locations for the mid segment arm and leg markers:

Marker label Definition Position on patient
Left lower limb markers
LTHI Left thigh Over the lower lateral 1/3 surface of the left thigh
LTIB Left tibia Over the lower 1/3 surface of the left shank
Right lower limb markers
RTHI Right thigh Over the upper lateral 1/3 surface of the right thigh
RTIB Right tibia Over the upper 1/3 surface of the right shank
Left upper limb markers
LUPA Left upper arm On the upper lateral 1/3 surface of the left arm (Place asymmetrically with RUPA)
LFRM Left forearm On the upper lateral 1/3 surface of the left forearm (Place asymmetrically with RFRM)
Right upper limb markers
RUPA Right upper arm On the lower lateral 1/3 surface of the right arm (Place asymmetrically with LUPA)
RFRM Right forearm On the lower lateral 1/3 surface of the right forearm (Place asymmetrically with LFRM)

Remember your Right Back marker

If you are using the Plug-In-Gait full body marker set ensure you remember your right back marker! This marker’s job is to help Nexus discern the left and right side of your subject.

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