GL: compass calculations

[Henry Quigley]

Tommy,

That must be a very, very old wives tale because anyone who would go
to sea these days without at least a handheld battery operated GPS is a
lunatic.

Henry

 


----- Original Message ----
From: John & Judy Gill
<jjgill at twojscom.com>
To: circumnavigate06 <circumnavigate06 at bellsouth.net>
Cc: great-loop at lists.samurai.com
Sent: Wednesday, September 23, 2009 10:22:26
AM
Subject: Re: GL: compass calculations

Tommy,

A minute of Latitude is
equal to a mile, but this does not equate to degrees on a compass because the
triangle gets larger the greater the distance.  So you would have to know how
many miles the projected run is.  The best thing to do is (1) calibrate your
compass and make a deviation table, (2) get a good GPS and learn to put in way
points -- that way you will know your Lat and Lon and whether you are staying
on course.

John

======================================
On Sep 21, 2009, at
3:25 PM, circumnavigate06 wrote:

> Hello,
> 
> There was a discussion in the
marina this morning about a fellow that cruised
> from Charleston, SC to
Bermuda and missed the islands entirely because his
> compass was not properly
calibrated.  The next conversation of course, led to
> how many degrees you
could be off course and still not miss Bermuda..
> 
> Well, I listened to all
these professional cruisers conjure up their ideas and
> thought that it might
not be safe to be on their boats!  I then realized that
> I also didn't know
the formula for calculating this and as we loop and cross
> Lake Michigan and
other big bodies of water, including the big bend section of
> the Gulf,
perhaps we all should take a few minutes and see what we really know
> about
this and maybe when it comes to crossing big water, we will feel more
>
comfortable knowing that we all can calculate these measurements.
> 
> So how
about it navigators, what is the formula for calculating how many
>
feet/meters/miles we are off for each degree of distance, at any distance
>
away?
> Tommy
> 
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