The Polhemus Liberty tracking system comes with a distortion sensing feature. The LED at the housing indicates three different distortion levels:
- Steady green: System operational with a good quality magnetic signal. No distortion
- Flashing red/green: System operational with a marginal magnetic signal. Minor distortion
- Solid red: System operational with a poor magnetic signal. Significant distortion
The distortion levels (represented as 0, 1, 2) can be accessed via the response frame.
How should the distortion level be represented in the tracking data?
- Currently, Polhemus tracking data is always considered as valid (see mitkPolhemusTrackingDevice.cpp, line 210). If distortion level is 1 or 2, it could be invalidated.
- PolhemusTool also has a method SetTrackingError(float). The distortion level could be set here. Interpretation of the value can be done at a later stage.