Welcome to the NavList Message Boards.

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    Name or NavList Code:
    Email:
       
    Reply
    Re: Should all electronic navigation devices on a yacht be set to True or Magnetic?
    From: Lu Abel
    Date: 2009 Nov 21, 21:46 -0800
    By that reasoning, you would trust the oscilloscope blip-matching inherent in Loran-A with the automatic calculations of Loran-C or GPS?

    I don't mean to insult you, but the way electronic compasses do their compensation is to measure magnetic direction as the boat circles through 720 degrees.   Making just one reasonable assumption -- that the boat's angular velocity is constant -- a deviation table can be created.  It's not a whole lot different from the way one creates a deviation table or a Napier diagram the old fashioned way.

    Having said all that, I firmly believe that one should at least once do a manual deviation table.   Why?   Because the one thing that this method can't detect is whether the lubber line (whether on a traditional compass or its equivalent in an electronic compass) is aligned properly with the boat's keel.  On my otherwise high-quality boat, it wasn't until I created a deviation table that I discovered that my lubber line was out of alignment by a couple of degrees!   (with a steering-pedestal compass it's hard to see if the lubber line is aligned with the tip of the bow -- especially since there is this vital propulsion component called the "mast" in the way).

    For those unaware, if one creates a plot with 0-360 on the horizontal axis and deviation on the vertical, deviation should form a sine wave symmetric around the X-axis.   Vertical displacement means the lubber line isn't aligned with the keel.

    Greg Rudzinski wrote:
    The corrections aren't displayed or quantified in any way. I prefer a
    deviation table.
    
    On Nov 21, 8:21 pm, Lu Abel <lu...@abelhome.net> wrote:
      
    Greg Rudzinski wrote:
        
    New units today are suppose to
    automatically correct for deviation after circling a few times. A
    feature which I would find hard to trust.
          
    Greg
          
    Why?
        
    
      

    --
    NavList message boards: www.fer3.com/arc
    Or post by email to: NavList@fer3.com
    To , email NavList+@fer3.com
       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Get a NavList ID Code

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    A NavList ID Code guarantees your identity in NavList posts and allows faster posting of messages.

    Retrieve a NavList ID Code

    Enter the email address associated with your NavList messages. Your NavList code will be emailed to you immediately.
    Email:

    Email Settings

    NavList ID Code:

    Custom Index

    Subject:
    Author:
    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site