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The advantage of performing all one's chartwork and calculations in
degrees True is that it reminds you that your magnetic compasses are
not necessarily reading Magnetic, unless they have been compensated
exquisitely well.

My small sailboat had no electronics until the late 1990's when I
bought a hand-held GPS. But from the first day I owned her I was
forcefully reminded of the need to allow for compass error. The
bulkhead-mounted steering compass was right over the engine's
starter/generator. When I fired up the Petter, the compass swung
5 degrees east. So, not one, but two Napier diagrams are stapled
inside the cover of my workbook.

[and although I'm sure it has nothing to do with age, I'm finding
that with each passing year the inner Magnetic ring of a coastal
chart's compass rose is harder to read than the outer True ring]

 -- Peter Smith

On Monday, November 16, 2009 8:16 PM,
David H. Smith  said:
> When a yacht is first fitted with a GPS, I believe most owners choose
> to set it to "Magnetic Heading" so that when comparing the bearing to
> the steering compass, only deviation has to be considered.  However,
> in a short time, the amount of electronic navigation instruments
> grows and grows.  A fluxgate compass along with an autopilot and
> electronic wind indicators get fitted.
> Then are added a radar, a second GPS chartplotter, a handheld GPS, a
> PC chartplotter, an AIS and an AIS display unit.
> So eventually we have aboard a yacht almost a dozen navigational
> instruments (along with paper charts) capable of being configured to
> "True" or "Magnetic" and just two instruments - the steering compass
> and the handheld compass not being able to give a "True" bearing
> readout The steering compass and handheld compass are now far less
> important than they used to be, (but are vital if the power fails or
> in emergencies).
> Information given on charts, in tide tables and other publications
> are all in "True" bearings.   It seems to me that the traditional
> way of recreational sailing yachts having all electronic bearings
> displayed as "Magnetic" or "Compass", may not now be the most
> sensible thing.

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