Saturn 2007 Ion Owner's Manual page 127

Compass Variance
The mirror is set in zone eight upon leaving the
factory. It will be necessary to adjust the compass
to compensate for compass variance if the vehicle
is outside zone eight. Under certain circumstances,
as during a long distance cross-country trip, it will
be necessary to adjust for compass variance.
Compass variance is the difference between earth's
magnetic north and true geographic north. If not
adjusted to account for compass variance, your
compass could give false readings.
To adjust for compass variance:
1. Find your current location and variance zone
number on the following zone map.
2. Press and hold the compass/temperature
button for six seconds until a zone number
appears in the display.
3. Press the compass/temperature button on the
bottom of the mirror until the new zone
number appears in the display. After you stop
pressing the button, the display will show a
compass direction within a few seconds.
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