GPS Receiver as an electronic compass

All GPS receivers can tell you which direction you’re heading — that is, as long as you’re moving. The minute you stop, the receiver stops acting as a compass. To address this limitation, some GPS receivers incorporate an electronic compass that doesn’t rely on the GPS satellites.

Operation
Like with an old-fashioned compass, you can stand still and see which direction your GPS receiver is pointing toward. The only difference is that you see a digital display onscreen instead of a floating needle. On some GPS receivers, you need to hold the unit flat and level for the compass to work correctly. Other models have a three-axis compass that allows the receiver to be tilted.
Paying attention to these factors can improve the performance and convenience of an electronic compass:

• Magnetic fields: Metal objects, cars, and other electronic devices reduce the accuracy of any electronic or magnetic compass.
• Battery life: Using an electronic compass can impact battery life. Some GPS receivers have settings that turn off the compass or only use it when the receiver can’t determine a direction from satellite data.

Calibration
Electronic compasses need to be calibrated whenever you change batteries. If your GPS unit has an electronic compass, follow your user guide’s instructions to calibrate it. Usually, this requires being outside, holding the GPS unit flat and level, and slowly turning in a circle twice.