Re: [Paddlewise] Compasses

Bob Volin wrote:
> 
> Peter Chopelas wrote,
> 
> <snippity>
> > When I learned about nautical navigation I was surprised to learn that
> > there is no need to ever concern yourself with declination because the
> > charts are all set up be able to use magnetic north exclusively (perhaps
> > the USGS who makes the land maps could learn something from the nautical
> > charts).  If you never intend to use the hand held compass for land
> > navigation then absolutely you do not need or want to worry about
> > declination, it would only serve to confuse you.
> 
> Would you explain your reasoning further, Peter?  I know that the compass
> rose on a nautical chart shows both true and magnetic, but the hash lines
> (?) on these charts are aligned to true north/south, east/west.  So it seems
> to me that one has to pay close attention to variation on a nautical chart.
> Of course, if you have a Nav-Aid, everything is much easier (I have no
> connection with the good Dr. Sutherland).

A quick and dirty method which avoids this problem is to lay out parallel lines
of magnetic north on 3-8 cm separations.  This allows taking "good enough"
*magnetic* bearings directly off the chart.

I have a Weems and Plath device which resembles a monster protractor adapted to
using such lines for taking accurate bearings off the chart.  It is not very
useful in a jouncy cockpit, but it works well the night before a paddle for
laying out the bearings you expect to need.  I think most of what I do is
described in Burch's book.

-- 
Dave Kruger
Astoria, OR
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