When an MTi is placed close to or on an object that is either magnetic or contains ferromagnetic materials, the measured magnetic field is distorted (warped) and causes an error in the computed yaw. The earth magnetic field is altered by the presence of ferromagnetic materials, permanent magnets or power lines with strong currents (several amperes) in the vicinity of the device. The distance to the object and the amount of ferromagnetic material determines the magnitude of disturbance introduced. Errors in estimated yaw due to such distortions can be quite large, since the earth magnetic field is very weak in comparison to the magnitude of the sources of distortion.
There are several ways to mitigate effects. These are described in the following BASE-articles and
Also consider reading this BASE-article first when you see large heading errors: https://base.xsens.com/hc/en-us/articles/202313502-Reasons-why-the-heading-is-not-stable-or-incorrect
- Magnetic Field Mapping -- https://documentation.xsens.com/magnetic_field_mapper_documentation
- In-Run Compass Calibraiton -- https://base.xsens.com/hc/en-us/articles/213588029-In-run-Compass-Calibration-ICC-and-Representative-Motion
- Gyro Bias Estimation -- https://base.xsens.com/hc/en-us/articles/203307252-Bias-repeatability-of-gyroscopes
- Active Heading Stabilization (AHS) -- https://base.xsens.com/hc/en-us/articles/210133105-Use-of-Active-Heading-Stabilization-AHS-in-MTi