Casio WSD-F10 User Manual page 51

To lock the direction
You can use Compass to lock the indicated direction to help you maintain a
specific bearing while trekking, etc. While the watch's 12 o'clock position is
pointed in the direction you want, tap the touch screen.
* If the watch's 12 o'clock position deviates from the locked direction, the
amount of the deviation will be indicated in blue, as shown here.
To unlock a direction, tap the touch screen again.
Compass Calibration (Magnetization Correction)
When the message "Perform magnetization correction." appears on the
compass screen, it means that you need to perform magnetization correction
of the watch. Move your arm so the watch faces front, back, left, and right. An
animated message will appear on the watch display to give you an idea of
how you need to move the watch. Keep moving your arm until the message
disappears, indicating that magnetization correction is complete.
Note
The watch normally performs magnetization correction automatically. You
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only need to perform the above operation when the message appears.
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