Automatic Identification of Markers (AIM)

Automatic identification of trajectories in the QTM software is performed by a module called AIM (Automatic Identification of Markers). The AIM model is created from identified files and can then be applied to any measurement that captures similar motions with the same marker set. This makes AIM very flexible and powerful - any motion can be made into an AIM model.

How AIM identifies trajectories

AIM identifies trajectories from angles and distances between markers. In the AIM model QTM has saved the angle and distance ranges of added measurement files. This is the reason why it works better when you add more measurements since the AIM model will then include more movements. When the model is applied AIM tries to find the solution that fits these ranges the best.

There are a few limitations to AIM that are good to know:

  • AIM does not work on only two markers. The main reason is that AIM works in local coordinates, i.e. it does not take into account whether "marker x is to the left of marker y". AIM only cares about "what location marker x has compared to the locations of markers y and z". This means that there is no left/right, over/below or in front of/behind in the model.
  • AIM needs to have movement in the first file used to create the model. Otherwise AIM will not identify the connections between markers in the AIM model, since they are based on the shortest possible distances between markers.
  • AIM looks for the best solution in each frame and then joins the solutions. This means that AIM will join and split trajectories depending on the AIM model so that you get the best match. The measurement subject can leave and enter the volume and AIM will continue to join the trajectories.
  • Because AIM is working with relations between markers, all of the markers in the model file must be included in the measurement to ensure that all of the trajectories can be identified. E.g. if a marker on the shoulder disappears for a long time it is difficult for AIM to find the arm.

For information about how to create and use AIM models, see the following chapters.