Cadillac 2000 Seville Owner's Manual page 112

The mirror can be calibrated in one of two ways:
D
Drive the vehicle in circles at 5 mph (8 km/h) or less
until the display reads a direction, or
D
Drive the vehicle on your everyday routine.
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 you live 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. Use the COMPASS side of the button located at the
bottom of the mirror. Press and hold COMPASS
until a zone number appears in the display.
2. Find your current location and variance zone number
on the following zone map.
2-52
3. Press COMPASS 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 "C" and will need recalibration.