Introduction to calibration

The QTM software must have information about the orientation and position of each camera in order to track and perform calculations on the 2D data into 3D data. The calibration is done by a well-defined measurement procedure in QTM. Calibration is, however, not needed for a 2D recording with only one camera.

There are two methods that can be used to calibrate a camera system:

• Wand calibration

  The most common type of calibration, see chapter Wand calibration method.

• Fixed camera calibration

  A special type of calibration mostly for large volumes with cameras mounted in fixed positions, see chapter Fixed camera calibration method.

The following items are important to think about before the calibration:

• Make sure that the capture area is free from unwanted reflections.

  • The cameras should be setup correctly, see chapter Optimizing the camera settings.

  • Follow the procedures for removing unwanted reflections, see chapter Removing unwanted reflections.

• Before the calibration make sure that the calibration settings are correct on the Calibration page in the Project options dialog, see chapter Calibration.

• When using Wand calibration it is important that the camera system have been placed correctly to achieve a high-quality calibration, see chapter Camera positioning.

  • For Fixed camera calibration the cameras should be mounted in their final, known positions before the calibration.

It is recommended that the motion capture system is calibrated regularly, for example before each measurement session, to make sure that the captured data has high quality.

• Regularly check that the calibration is OK during long measurement sessions.

• There is an automatic check if the cameras have moved, which is activated on the Calibration quality page in the Project options dialog, see also chapter Calibration quality warning.

A calibration starts with the Calibration dialog, see chapter Calibration dialog. Click on the Calibration icon to open the dialog.

Each calibration is saved in a QCA file in the Calibrations folder in the project, see chapter Project folder. The file name contains the date and time of the calibration.