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Re: CYOA - Re: Hand held GPS

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  • lookoutnw@comcast.net
    SADULU ?  Nope, Taking Fire out of the Old lady, Yep, only mine still has a lot of fire left in her, especially when I screw up. ... From: Jim Muri
    Message 1 of 12 , Dec 26, 2008
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      SADULU ?  Nope, Taking Fire out of the Old lady, Yep, only mine still has a lot of fire left in her, especially when I screw up.

      ----- Original Message -----
      From: "Jim Muri" <irumrj@...>
      To: columbiasailingyachts@yahoogroups.com
      Sent: Friday, December 26, 2008 7:59:29 AM GMT -08:00 US/Canada Pacific
      Subject: Re: CYOA - Re: Hand held GPS

      Actually, I meant declination in the common parlance, as in "Angle of divergence between true north and magnetic north."  I've been away from the vocabulary for a long time, and in the old days I also had to factor in declination for grid north.  Yes, in the use of military maps set up in Mercator projections, there were actually three norths - true, grid, and magnetic.  And each had their own divergences.  We had to declinate our aiming circles (I was in the artillery) to correspond to local grid / magnetic divergence.  Our friendly survey folks would actually set up declination points for us to do that.  Ask Jim Lussier about that, he was one of those guys we depended on.  I'll bet he can even remember what "SADULU" stands for.  <G>
       James R. Muri

      Novelist, Sailor
      BUY: My e-Novels at http://blizzardguy.com/venture/
      SITE: http://blizzardguy.com
      BLOG: http://theostrichkiller.blogspot.com

      From: Joel <cruiser6003@...>
      To: columbiasailingyachts@yahoogroups.com
      Sent: Thursday, December 25, 2008 11:17:58 PM
      Subject: CYOA - Re: Hand held GPS

      I'm sure you meant Variation is printed on the chart along with
      annual drift. Deviation is boat/compass induced and unique to each
      Compass installation. A compass deviation card should be prepared for
      each compass onboard and is prepared using a method called "swinging
      the compass" and is best done on ranges set up for it.

      T-V-M-D-C-A- W: True Virgins Make Dull Companions At Weddings
      C-D-M-V-T-A- E: Can Dead Men Vote Twice At Elections

      Joel Wilkins
      m/s Miss Magoo
      C-45, #98
      S. Pasadena, FL

      --- In columbiasailingyach ts@yahoogroups. com, Jim Muri <irumrj@...>
      > I don't know of one that won't do that, Phillip.  On the set-up
      menu you get to select which north to use, true or magnetic. 
      And every nav screen will display your COG (course over ground)
      which, of course, is usually different than the direction your boat
      is pointing.
      > But beware of calibrating your compass based on GPS readings. 
      You'll be comparing apples to oranges.  The GPS will display your
      course over the ground, but your compass tells you in which direction
      the boat is pointing.  The two are seldom exactly the same, and may
      differ by thirty degrees or more.
      > To get the mag deviation in your area, simply refer to the nautical
      chart.  It'll have it overprinted right there, usually in more than
      one place.  Even better, it'll tell you how much 'drift' to expect
      annually.  So look at the chart datum (date), do the math, and voila.
      > Speaking as a heretic, why bother with a compass at all if you have
      GPS?  Like the sextant and traditional nav station, it's an
      anachronism of little practical value - good in the antique stores,
      but not so good on boats anymore.  Your compass won't keep you from
      running into rocks in the fog, but your GPS and charts will.
      > Dr. Dave once told this forum that offshore he seldom looked at the
      compass; maybe once a day.  Only when he got close to his destination
      did he consult it more frequently - and that was in the days before
      GPS was routinely available, 24/7.
      > Oh, I know I can expect a LOT of flak about those last two
      paragraphs.  Merry Christmas, Everyone!!!
      >  James R. Muri
      > Novelist, Sailor
      > BUY: My e-Novels at http://blizzardguy. com/venture/
      > SITE: http://blizzardguy. com
      > BLOG: http://theostrichki ller.blogspot. com
      > ____________ _________ _________ __
      > From: palm_atoll <palm_atoll@ ...>
      > To: columbiasailingyach ts@yahoogroups. com
      > Sent: Wednesday, December 24, 2008 8:14:26 PM
      > Subject: CYOA - Re: Hand held GPS
      > Does anyone know if there is a handheld gps that will read out
      > direction of travel in degrees digitally. It would be nice to be
      > to select between true north, and mag north and get a digital
      > direction of travel. I can compare it with the compass reading and
      > a compass deviation.
      > thanks
      > Phillip
      > [Non-text portions of this message have been removed]



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