Dodge 2007 Ram Pickup 3500 - Manual (Page 185)

Compass Variance is the difference between magnetic
north and geographic north. In some areas of the country,
the difference between magnetic and geographic north is
great enough to cause the compass to give false readings.
If this occurs, the compass variance must be set according
to the Compass Variance Map.
UNDERSTANDING THE FEATURES OF YOUR VEHICLE 185
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