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Subject: Re: [Nml] DR
From: Dan Hogan (dhhogan@XXX.XXX)
Date: Mon Feb 22 1999 - 18:24:45 EST
Millard:
> Silicon Sea,
[Snip problem stuff Q2]
> I must admit that these problem have been a great learning experience
> for me. If one uses the current to get the DR is it really DR or estimate
> position (EP). Bowditch - Dead reckoning (DR) determines position by
> advancing a known position for courses and distances. A position so
> determined is called a dead reckoning (DR) position. It is generally
> accepted that only course and speed determine the DR position. Correcting
> DR position for Leeway, current effects and steering error results in an
> estimated position (EP)
My fault. We agreed during the legs from Maldives to Sydney to call DR=
no current and EP=current. Will change my terminology. I'm having a
hard time with this since in all my sailing all I used the term DR for
everything.
[Snip]
> To get DR on the Celesticomp V it asks for Departure Lat & Lon, Steered,
> Speed, Var&Dev and Turn Point time. I guess the "Steered" always did
> drive me little crazy in the DR program because there is a program that is
> called STEER/CUR which give one the Course to Steer if one has Desired
> Course (TC) Var&Dev, Log Speed, Current Dir, and Current Velocity. So if
> I use the "Steered" Compass course from the STEER/CUR in my DR program I
> actually get EP not DR.
The problem is that Bowditch has been made "politically correct", a
lot of earlier navigation books, texts, and methods use the earlier
definitions, I.e. Course-to-steer, Course Made Good.etc.
In my hard drive double crash of '98 I lost most of my tips and hint
for Silicon Sea. If anyone has the definitions list please post it.
Any how from now on:
DR = position based on distance = time x speed
EP = DR plus the correction for current.
Dan Hogan WA6PBY
dhhogan@XXX.XXX
Catalina 27 "GACHA"
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