From I Heart Robotics:
"While it may be obvious to some, as a practical matter, steel doors should be considered a serious navigational hazard to indoor autonomous micro air vehicles due to the effects of the magnetic fields. This problem is especially noticeable in hallways with several closely spaced steel doors.
The effects for these fields on the pose estimate should be considered when calculating the magnetometer's sensor error model for the Extended Kalman filter. Otherwise the sensor will have a noticeable negative influence on the EKF output.
One of the symptoms of this problem that you may experience is that the fused IMU yaw data is less accurate than the unfiltered yaw gyro data.
The door shown in the video is not located near any high current electrical wiring and multiple, but not all, steel doors in several locations exhibited this behavior."
Comments
First I went near an exterior door and saw the sane errors. The i opeont the door 90 deg. and saw now error. Went close to my fridge and saw a really strong effect. The it hit me. Its not the steel door but the magnetic srtip door seals. I confirmed this on my open front door. The DARPA types need to remember this when developing hovering UAV's that are designed to pick locks on entry doors so the can fly in and search for "bad guys" :)