In all capture modes, if you plan to capture global angles, to ensure that the IMU sensor data is stable and to minimize drift, at the start of every trial, you must calibrate the IMU sensors.
To calibrate the sensors:
- Start streaming global angles. (If you're not sure how to do this, see Start Capture.U and choose a capture mode.)
- Wave the sensor in a figure-of-eight for at least 10 seconds.
Put the sensor on a flat surface and spin it through two full rotations, ensuring that it rotates through all three axes during the motion.
To avoid any unwanted influence on the sensor, avoid placing it in proximity to anything metallic.
- Wait until the data has stabilized.
In Real-Time Insight and AR Visualization modes, you can observe that X angle is 0 and the Y angle is 0 (the figure-of-eight provides enough information for the sensor to self-calibrate). However, the Z angle may have a non-zero value, depending on how it is rotated to the magnetic north.
- Rotate the sensor on the flat surface until Z is also 0.
- If you plan to capture global angles, after the sensors are attached to a subject, allow a few seconds for onboard calibration to initiate before starting the movement that is to be captured.