NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Should all electronic navigation devices on a yacht be s...
From: Jeremy C
Date: 2009 Nov 17, 11:07 EST
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From: Jeremy C
Date: 2009 Nov 17, 11:07 EST
I think i'd stick with "true" bearings and such as it is less
confusing. Magnetic devices are good in emergencies, but considering that
declination varies with heading and energized equipment, Variation changes with
position, and then there are "local magnetic anomalies;" it's safer to just use
an electric compass for heading.
Also, it's easier to plot true bearings on charts than magnetic. I
basically never use the compass roses on the charts. It's much easier to
use triangles or protractors based on the chart's grid without all the
calculations converting compass to true.
Jeremy
In a message dated 11/16/2009 8:16:40 P.M. Eastern Standard Time,
dhs@clear.net.nz writes:
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.
I would appreciate advice and opinions.
David.
New Zealand.
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