MyTrails can use your phone’s built-in magnetometer and accelerometer to simulate a compass. However, unlike a physical compass, phones need to be periodically calibrated to provide an accurate reading of the magnetic north bearing.

There are two methods (both need MyTrails to be running with the screen on – MyTrails disables the compass when the screen is off):

• turn the phone around each of its axes in succession; this is the most accurate method, but it takes a bit longer and there’s more chance of dropping it
• use a figure-8 movement; this is quicker but doesn’t always provide enough data for full calibration

Keep in mind that even after calibration, the compass is sensitive to interference: don’t place it next to ferrous metals.

Unlike a physical compass, MyTrails can automatically correct the magnetic declination to provide a reading of the geographic rather than magnetic north.

If the compass seems to rotate in the opposite direction of your real movement when you, please try using the toggle reverse compass hidden option.

In addition to the compass, MyTrails can use the GPS-derived heading, with the following caveats: it’s only active above 1m/s (too imprecise at slower speeds), and the GPS heading indicates the direction of your travel, not the direction the phone’s screen is pointing.

Another method, described by Google.

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