SUUNTO AMBIT3 SPORT - Manual (Page 20)

If you have already calibrated the compass and want to re-calibrate
it, you can access the calibration option in the options menu.
If the calibration is successful, the text CALIBRATION SUCCESSFUL is
displayed. If the calibration does not succeed, the text CALIBRATION
FAILED is displayed. To retry the calibration, press [Start Stop].
To manually start compass calibration:
1. Keep [Next] pressed to enter the options menu.
2. Select to GENERAL with [Next].
3. Scroll to Compass with [Light Lock] and select with [Next].
4. Press [Next] to select Calibration.
3.6.2 Setting declination
To ensure correct compass readings, set an accurate declination
value.
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