Prevent ghost markers

The typical cause of overlapping trajectories is spurious, or ghost, markers that are present during marker reconstruction. A ghost marker is a false marker reconstruction that appears as an additional trajectory very close to a legitimate marker trajectory. Ghost markers can be reconstructed if:

• The Nexus Core Processor settings are not optimized for the type of capture you are performing. For example, if a Reconstruction Minimum Separation is set too low, Nexus may reconstruct all detected marker positions rather than selecting only the best candidates.
  Depending on whether you want to adjust the Core Processor settings for offlline data or live capture:
  
  • If you don't want to recapture the trial you are processing, adjust the Offline processing parameters and reprocess the existing trial to see if Nexus resolves the overlapping trajectory. You set offline processing parameters in the Core Processing operations in the Pipeline Tools pane.
  • You may also need to evaluate whether future captures will be similar enough to the current trial conditions (such as subject movements, marker placement and movement, number of cameras, etc.), that adjusting the Live Core Processor settings will eliminate the issue in future. To set live processing parameters, in the System Resources pane, click on Local Vicon System and in the Properties pane go to the General section and select the required Processing Output Level.
• One or more cameras need to be recalibrated, eg, if one or more cameras has been accidentally knocked since it was calibrated. For details, see Understand camera calibration refinement.
• Camera masking is inadequate or has not been performed. For details, see Mask unwanted reflections in the Vicon Nexus User Guide.

After you have addressed the above issues, reprocess the trial before proceeding.

If adjusting the reconstruction parameters and reprocessing do not produce a properly labeled trajectory, you may need to manipulate the trajectory sections manually.