1997 Pontiac Bonneville Owner's Manual - Page 135

Electronic Compass (Option) The earth's magnetic fieldis not always the same direction as true northas we know it. So, you must enter a zone number to tellthe compass the difference between magnetic and actual north. This tells the compass where inthe country you are driving The compass shows the zone number in use each time you turn your keyon. This is shown above. The number is turned off after a few seconds. The compass remembers your zone,so you only have to change it if you drive to a new zone on the map. The compass adjusts only a small amount for each zone, so you may not notice a difference if you drive from one zone to the next one, until you crossseveral zones. ' N Some vehicles are equipped with an electronic compass. As with all compasses, this unit senses the earth's magnetic field to show the direction the car is pointing. 2-82