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Jim,one more thought on this subject of APs and EPs etc.
A little experiment if you are interested.
If you have an A.H. and the conditions are such that you can attempt a round
of sights and you have the time take a gps reading of your pos.Set up the
horizon and useing the rules for spaced azimuths shoot 3 altitudes of 3
objects spaced over a period of time to simulate a real round of sights as
on a ship so as to obtain a fix.
Useing the sin-cosine method reduce all the sights and plot the intercepts
and azimuths on a plotting sheet from the gps(dr)position.
Turn the sheet over.
Useing the AP(whole degree)method use H.O. 229 or 249,reduce the same sights
and plot the corresponding intercept and Zn from each AP on the plotting
sheet.
You may also use 1 body and take 3 sights of it over a period of time.
Explain to me what you see on the plotting sheet.I'm interested in what you
observe between the 2 methods.


Actually,what you quoted from Bowditch '02 in your post today was basically
what Joel Jacobs quoted yesterday in his post about definitions.

My intent is not to give you a hard time.



-----Original Message-----
From: Navigation Mailing List
[mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM]On Behalf Of Royer, Doug
Sent: Friday, February 20, 2004 10:58
To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
Subject: Assumed positions and plots


Jim,I now understand what you are being taught.The course you are takeing
just seems to use differant terminology than what I'm used to.On that note
the following:
1.The method you are useing(being taught)is as good as the method I
use.You're comfortable useing it.
2.As Fred stated, in practice, useing the method you are being taught can
get the plotting sheet or chart rather messy or cluttered.
3.If you use reduction tables(H.O. 229 or 249)exclusively the AP is
differant than an EP or DR.As each AP for the round of sights is differant
due to each  body's LHA being differant.
4.When plotting the LOPs on the sheet useing an AP(whole degree argument)try
the following to reduce clutter.
Instead of marking seperate dr or ep positions corresponding to each cut and
plotting from such try plotting from each AP.By that I mean in the round of
sights advance(or retard)each AP instead of each dr.Because the vessel's
travel distance during the round won't exceed the 30' of arc tolerance
between the dr and each AP it will not effect accuracy.
Say you take around of 3 sights starting at 1800.The 2nd sight is at 1812
and the last is at 1823.Your course is 222* and your speed is 10 kt.The 1st
AP(1800) is advanced 3.8 mi at 222* and the intercecpt and Zn are plotted
from there.The 2nd AP(1812) is advanced 2 mi at 222* and plotted from
there.The 3rd AP(1823) is plotted from it's whole degree position.

   

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