Getting Directions CHC Proceed to Your Destination Without Having to Ask Someone 40 277

Recalibrate your bearings on electronic compasses as Stuart navigates a journey with an MCU-guided compass module leading the way. He tells us how to avoid magnetoresistive effect, and the difference between magnetic north and true north.

- Stuart Ball

I've been writing occasionally about sensors, this article is about electronic compasses. With modern GPS, it's easy to keep track of where you are, and a GPS can even tell you the direction you are moving - as long as you're moving. Some handheld hiking GPS units have a built-in electronic compass because GPS gives you your position but can only tell direction if you are moving; I have a hiking GPS with a built-in compass.

A lot of cars contain a compass with the direction displayed either on the dashboard or in a corner of the review mirror.

Handheld mechanical compasses have been around for centuries, of course. I still have one in my hiking backpack. A compass can be affected by nearby metal and other interfering items. I had a compass in a car years ago that tended to point to the engine block rather than pointing north. Mechanical compasses are also prone to break and obviously can't be incorporated into a vehicle dashboard display.

Sailing ships with steel hulls and mechanical compasses have historically had steel balls and compensating magnets to adjust for the magnetic effects of the ship's hull.

Normally a mechanical compass points to the north pole the magnetic north pole.

The magnetic north pole isn't quite the same as the geographical north pole. Sometimes it doesn't matter because you are using a compass to navigate between two visible points. Or else you just want a general north/ south indication, like the way the compass in a car just gives you a general direction at the 8 points of the compass (N, NE, E, etc.). But sometimes you want to know where true north is, and you want more precision than the 8 compass points. This is especially important in aviation. Of course, modern airplanes use GPS for navigation, but the FAA still requires a compass as a backup instrument.

DECLINATION