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Gold Winger

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Got this from a web site hope it helps.



Understanding 3 Axis Digital Compass Instruments:

A 2 axis compass must remain level (perpendicular to Earth's gravity) to avoid extreme errors in heading. 3 Axis Instruments deliver accurate heading at any attitude within their tilt ranges using electronic gimbaling calculated from 3 axes of magnetic sensors and a bi-axial tilt sensor. The orientation is corrected for magnetic distortion from magnetic sources and materials in 3-D. Mechanically gimbaled and 2-axis solutions cannot provide correction in 3-D. The instruments provide orientation data for all three angles: heading, pitch and roll.

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In general for gps applications as I understand it, the 3 axis units are much better at dealing with you tilting the unit and still giving a accurate compass reading. From what I have heard Magellan uses this system.


Garmin uses a 2 axis electronic compass in it's gps units and if my 76csx is any example it's very sensative to tilting the unit even small amounts. A small tilt of 1/4" on my unit will throw off a reading by +/- 10 degrees or more. 1/4" sounds like a lot but realize that's 1/8" at the front and 1/8" at the back that's pretty easy to do, and if you are trying to sight something up or downhill the measurements will be way off. My 76s seemed better at this, however it included a warning on the screen if you had the unit out of tilt, the 76csx does not have such a warning.

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