Fluxgate Compass Information

Simply a fluxgate compass uses electromagnets to sense or read the earth’s magnetic field to determine where north is. The electrical output from the compass is easily digitized for display and for use with other navigation equipment.

A fluxgate compass has two or more small coils of wire around a permeable magnetic material to sense the direction of the horizontal component of the earth’s magnetic field. This reading in an electronic form can be digitized and transmitted easily. The signal can be displayed remotely, and the signal can be used by electronic autopilots for course correction.  

The vertical component of the magnetic field can cause inaccuracies if the compass is not level. A fluxgate compass array is kept as flat as possible by mounting it on gimbals or using a fluid suspension system and electronic damping systems. This helps to ensure directional readings are adequately stable. Some compasses are 3-axis fluxgate magnetometers that provide a 3D flux vector. The magnetic heading is then derived from the flux on a plane perpendicular to gravity. This better compensates for pitching and rolling on a vessel.

If GPS systems are turned off by a government in time of war and a GPS becomes no functional, a fluxgate digital compass still works.

A gyro compass can also be integrated in to the navigation system and it will provide better accuracy against acceleration and heeling effects. They are also more accurate in high latitudes.

Fluxgate compasses and gyros complement one another nicely. One is not better than the other. The fluxgate provides a directional reference that's stable over the long term, apart from changing magnetic disturbances, and the gyro is accurate over the short-term, even against acceleration and heeling effects. At high latitudes, where the Earth's magnetic field dips downward toward the magnetic poles, the gyro data can be used to correct for roll-induced heading errors in the fluxgate output. It can also be used to correct for the roll and heel-induced errors that often plague fluxgate compasses installed on steel vessels.

Today’s fluxgate compass by itself is a good stand-alone compass for most situations. It can be integrated with other navigation systems as they are added.