Suunto D9 User Manual page 31

Calibration
Because of changes in the surrounding magnetic field, the Suunto D9 electronic
compass occasionally needs to be re-calibrated. During the calibration process, the
compass adjusts itself to the surrounding magnetic field. As a basic rule, you should
calibrate the compass whenever it doesn't seem to operate properly, or after replacing
the dive computer's battery.
Strong electromagnetic fields, such as powerlines, stereo speakers, and magnets can
affect the compass calibration. It is therefore advisable to calibrate the compass if
your Suunto D9 has been exposed to these fields.
NOTE
NOTE
To calibrate the compass:
When traveling overseas, it is recommended that you recalibrate
the compass at the new location before using it.
Remember to hold the Suunto D9 level during the calibration
process.
HOLD THE
DEVICE LEVEL
AND SLOWLY
ROTATE 360°.
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