NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Why Not To Teach Running Fixes
From: Joel Jacobs
Date: 2009 Dec 13, 12:48 -0500
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From: Joel Jacobs
Date: 2009 Dec 13, 12:48 -0500
John,
I do not believe in practice people using a running fix will ignore
set and drift of current in plotting or the affect of leeway in a sailing
vessel, or a vessel affected by a lot windage, if they have a reasonable way of
estimating these forces. I suggest the example Lu posted was
simplified for teaching purposes which gets students to understand the
basis concept which is a good thing.
If the force of offset is unknown, one way to do this is the use of "back
bearings" which are useful no matter what type of ship.
For the same reason, since you did not explain or show how you calculated
the vector offset in determining your EP 1 which you carry forward to EP
2, you must have also simplified it for clarity of illustration.
Just a thought,
Joel Jacobs
----- Original Message -----
--From: John KarlTo: NavList@fer3.comSent: Sunday, December 13, 2009 11:25 AMSubject: [NavList 11116] Why Not To Teach Running FixesAh, the traditions of the sea.
For all the talk on how to teach running fixes, here's my 2 cents
worth on why to not teach them at all -- they make no sense whatsoever.
The figure below shows that they operate under extremely ridiculous
assumptions: They assume that the estimated DR track perpendicular to
LOP1 is completely accurate and that the DR component parallel to LOP1
is completely without value. Can anyone on the List justify these two
assumptions??
I recommend using the Estimated Position (EP) concept shown in the
figure. It fully honors the new LOP2 while retaining the information
in the DR that is not contradicted by LOP2.
JK
--
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