Many Garmin GPS models come with compass information. Compass capability is commonly found with aviation, sport, hiking and marine GPS models. Compass information, in the form of a compass or pointer page menu, is rarely found on road GPS units. When a GPS unit includes a compass page, a rotating compass card appears with a display identical to that of a standard magnetic compass.
Garmin GPS units with compass capability do not contain an internal magnetic compass or magnetometer. The compass information is derived from the triangulation of multiple GPS satellites in orbit around the earth. A GPS receiver must acquire a minimum of three GPS satellites to determine latitude and longitude information, and therefore, to receive compass data on a Garmin GPS unit.
All GPS compass information is derived from one source, GPS satellite uplinks. Normal GPS operational limitations apply--the device must have a clear, unobstructed sky to receive strong signals from the orbiting GPS satellites. A GPS unit must be in motion for the compass to function because the direction the user is facing is determined by the relative motion of the latitude and longitude coordinates.
Garmin GPS units with compass capability experience lower magnetic dip error than standard magnetic compasses. Magnetic dip errors occur because lines of magnitude do not parallel the Earth's surface, causing the magnetic compass to show erroneous bearings during turning or acceleration. Another magnetic compass error called oscillation is minimized when using a GPS compass. Oscillation error is the natural movement and instability of the magnetic compass.
Garmin GPS units that feature a compass will include either a "compass page" or a "pointer page." The compass or pointer page will show the compass card and a lubber line. The lubber line is a vertical reference line extending from the top-center portion of the compass that shows your current direction.
Select a destination to most efficiently use the GPS unit's compass capability. After you have selected a destination, the compass page will now depict an arrow in the center of the page pointing to the destination's direction from your current location. Additionally, the compass page will display the distance, time, and speed to your destination.
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