NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: GPS & Magnetic Bearings
From: Rodney Myrvaagnes
Date: 2003 Feb 9, 19:27 -0500
From: Rodney Myrvaagnes
Date: 2003 Feb 9, 19:27 -0500
On Mon, 10 Feb 2003 08:53:27 +1100, Peter Fogg wrote: >Brooke Clarke wrote: > >> ... the magnetic deviation if ... > >> Jared Sherman wrote: >> >> ... the GPS ... deviation data ... > >I'm not sure if this is due to different countries using different terminologies but I learned that the compass difference due to the magnetic poles not being aligned with the geographic poles is called compass variation and local effects (like an iron engine block) about the vicinity of the compass is known as compass deviation. > >So: GPS can have no idea of compass deviation (?) but may, we are learning, have various built in systems to correct for compass variation (?). I guess the real bottom line is that GPS may indicate true bearing which is a mighty useful thing to know. You are correct, but since the deviation doesn't affect the GPS it has no use for deviation data. If its variation table is still good it will be able to show a deviation-free magnetic course. It will always be able to show true course if the vessel is moving. Rodney Myrvaagnes NYC J36 Gjo/a "WooWooism lives" Anon grafitto on the base of the Cuttyhunk breakwater light
