NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Automatic deviation calculation by electronic compasses
From: Frank Reed
Date: 2009 Dec 9, 22:51 -0800
From: Frank Reed
Date: 2009 Dec 9, 22:51 -0800
Digital compasses today certainly include the ability to generate their own internal calibration tables. I've seen this in action on a new iPhone. When it needs to re-calibrate, a little notice comes up with a graphic telling the user to wave the phone around in a figure-eight pattern. And no, I have no idea how that works, and I think that's a big part of the problem in these discussions. NO ONE on NavList knows how these devices work. But if you would like to wrap your brains around this issue a little more, despite being technically off-topic for our traditional navigation group (not a complaint, merely an observation), have a look at the technical specs on this rather pricey little digital compass chip from PNI: http://www.pnicorp.com/products/family/fieldforce/tcm-xb Apparently, for a thousand bucks per chip, you can get a pointing accuracy (after a certain calibration sequence) of 0.3 degrees r.m.s. If you browse this site, there's lots of interesting talk about calibration in various conditions and it seems at least somewhat clear to me that they do all of this by detecting field gradients, however the details usually end with the phrase "proprietary algorithms". -FER -- NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To , email NavList+@fer3.com