NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sextant/3 Arm Or Gyro Bearing Pmp Plot
From: Jeremy C
Date: 2010 Nov 25, 03:42 EST
From: Jeremy C
Date: 2010 Nov 25, 03:42 EST
I think that you misunderstood what I was saying Byron. I was
saying that for me to plot the three bearing lines at anchor is much quicker
with a 3 armed protractor than my normal parallel rulers/triangles that I would
otherwise have to use. I don't know about a plotting machine as I've never
been on a ship so equipped.
I am also doing this alone and am not using a sextant at all. I
take 3 bearings with a bearing circle, find the angular differences of
bearing between them, set the arms, and overlay it on the chart.
My other option would be to take the three gyro bearings, apply the GE
& Repeater error, then plot them individually. This process takes me
much longer for the scale chart I am using as I need a long straight edge as
well as my triangles.
I am not sure why you would need to "evaluate" the 3 armed protractor
bearings. The only errors that come into play are a scale error in
either the repeater circle or protractor, or an error in observation.
Compass error should play no part as the basis of the observation is relative
angles. If fact, to make the math the simplest, taking relative bearings
with heading as zero is actually the way to go.
I am sure a plotter and bearing team (consisting of more people than are on
my bridge during maneuvering) can certainly lay a position quickly, but that is
not an option with us. Then again, we aren't using a 3-armed
protractor except at anchor either.
Jeremy
In a message dated 11/24/2010 7:00:10 A.M. Central Asia Standard Tim,
byronink@netzero.com writes:
Someone said that the sextant 3 arm is faster
than bearing plot. My experience is that is incorrect. Also I say that the 3 arm can not be evaluated as to how accurate the fix is as easy as the bearing plot.. The 3 arm can be very accurate and quick, but will take the back seat to a gyro bearing team and a plotter.Give me your augment?
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