Calibration: Body

In order to identify a three dimensional arrangement of markers as a “target” (or “rigid body”), i.e. as an object to be tracked, the geometry of this marker configuration has to be calibrated. In other words, the target is shown to the tracking system and the special geometry of marker positions is stored in a data file “Body?.txt”, which is the base for target identification and tracking. This fast (30 sec) and simple calibration process is included in the DTrack software.

The identification of a rigid body is based on the distances between single markers in a target. This means, each target has to show a unique set of marker distances. In the DTrack2 software two distances differing by less than a certain threshold value (in standard setups 2 mm) are regarded as the same distance. As a consequence, for two different targets as many distances as possible have to differ by more than the threshold value. The same condition has to be applied for the marker distances within one target. In the “Body?.txt” files the marker distances are listed, in order to allow a first, course evaluation of target geometries.

After a new room calibration a recalibration of targets is not necessary. Target recalibration has just to be done if the target geometry has been changed.