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Subject: Re: Leg 83
From: Dan Hogan (dhhogan1@XXX.XXX)
Date: Tue Sep 24 2002 - 09:50:51 EDT
Arthur:
Using the "really old way of navigation" is prone to errors. If the
arithmetic is OK then Q2 TC should come out close to 285d. After that the
most accurate way to manually calculate CC is using a vector plot.
P.S. On a previous post to you I noted that there ia a possible error in my
CelestNav v. 2.3.2 Mercator calculations.
The DR problems for Silicon Sea are calculated with Navpo93 from NAVIG which
are Rhumb Line. I double check them with an HP 32SII Mercator program from
"The Calculator Afloat" by Shufeldt & Newcomer.
On 22 Sep 2002, at 22:33, Arthur Pearson wrote:
> Peter et. al.
>
> Many thanks for these exercises, they are a great project now that the
> boat is put away for the winter and we have to find another way to keep
> the skills fresh.
>
> I am consistently getting 290d True for Q2 below. I am using 1958
> Bowditch Traverse tables and I have worked the problem as a Mercator
> Sailing (looking up the MP's of the two latitudes to get m, dividing
> that into DLo, using that ratio to get a NW bearing) and as a Mid
> Latitude Sailing (using DLo at 19d and 20d to interpolate for departure
> (p) and dividing by change in latitude (l) and using that ratio to get a
> NW bearing. Both methods bring me to 290d as does my PalmPilot running
> CelestNav for a Mercator Sailing. In no case can I find my way to 285d.
> I concur that the adjustment for current is about -1d and the combined
> variation and deviation is -11d, bringing me to a course to steer of
> 278d.
>
> Where have I strayed?
>
> Arthur
Cheers
-Dan-
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