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    Re: Cannot dispense with the assumed position at sea
    From: Dave Weilacher
    Date: 2004 Feb 19, 14:04 -0800

    I had just interpreted his original proposition to mean DR.  It seemed to be 
    the context he was using it in.
    As to the running fix being a misnomer, I disagree.
    A running fix has the same kind of relationship to a fix that a near-miss has 
    to a miss.  They are both fixes and both misses repectively.  There is just a 
    quality difference between them.
    With a running fix, you are advancing or retarding a line of position based on 
    the presumption you know your course and speed resulting in whatever error 
    that induces.  A fix leaves that out because of the nearly simultaneous 
    An argument that goes on in our local area is that a running fix is made up 
    from two and only two lines of position.
    They conclude from this that if you make a morning, LAN, and afternoon sight, 
    then advance the morning sight and retard the afternoon sight, it gives you a 
    noon fix, as opposed to a noon running fix.
    -----Original Message-----
    From: Joel Jacobs 
    Sent: Feb 19, 2004 1:44 PM
    Subject: Re: Cannot dispense with the assumed position at sea
    These are definitions that I learned years ago. They may or may not be
    A DR is a position derived from solving time, speed, distance from you last
    An AP is an arbitrary position selected to be an entering argument in the
    sight reduction process. You do not need an AP if you are using a computer
    or software. If you use most tables you need an AP. I think you may not need
    an AP if you use HO 211, Ageton.
    An EP is a DR adjusted for the affects of wind, leeway, and or current.
    A FIX can only be determined from two or more near simultaneous sights, with
    the level of confidence increasing , with the number of different bodies
    IMO, a running FIX based on the above definition is a misnomer.
    At least that's what I recall.
    Joel Jacobs
    ----- Original Message -----
    From: "Royer, Doug" 
    Sent: Thursday, February 19, 2004 4:21 PM
    Subject: Re: Cannot dispense with the assumed position at sea
    > -----Original Message-----
    > From: Royer, Doug
    > Sent: Thursday, February 19, 2004 12:18
    > To: 'navigation-l@listserv.webkahuna.com'
    > Subject: RE: Cannot dispense with the assumed position at sea
    > All positions at sea may be called assumed positions!They are all where
    > were,not where you are.Errors or conditions while shooting the sight or
    > reduceing the data may have you not where you believe you were.Nothing in
    > real life is perfect.
    > Perhaps I missunderstand what you are trying to convey.Perhaps it is a
    > function of wording between what you call an assumed pos and my
    > For me an assumed pos or positions are what one uses in lue of a dr or ep
    > pos when reduceing a round of sights.An AP is the position chosen to
    > the sight instead of the dr or ap pos.
    > One chooses the assumed pos to be the closest whole degree of Latitude of
    > the dr or ep latitude.The longitude of the AP is chosen by useing the
    > degree of longitude of the dr or ep,subsituteing the ' and " of the body's
    > LHA for the " and " of the dr or ep longitude.One chooses this assumed
    > longitude to stay with in 30' of arc of the dr or ep longitude.
    > You can then enter reduction tables or solve for the nav triangle to find
    > the intercept and AZ thus finding the LOP or the fix if a round of sights
    > were taken.
    > One can also use the dr or ep pos to solve the nav triangle with out
    > an AP.
    > Am I not understanding what you wrote or is it a matter of definitions?
    > A celestial EP will only be as good as the AP. The more one has to guess
    > the AP, then the less confident one can be about estimating where the
    > is on the celestial LOP.
    Dave Weilacher
    .US Coast Guard licensed captain
    .    #889968
    .ASA instructor evaluator and celestial
    .    navigation instructor #990800
    .IBM AS400 RPG contract programmer

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