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    Re: Cannot dispense with the assumed position at sea
    From: Joel Jacobs
    Date: 2004 Feb 19, 16:44 -0500

    These are definitions that I learned years ago. They may or may not be
    current.
    
    A DR is a position derived from solving time, speed, distance from you last
    position.
    
    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
    selected.
    
    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" 
    To: 
    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{at}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
    you
    > 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
    definition.
    > 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
    reduce
    > 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
    whole
    > 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
    useing
    > 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
    at
    > the AP, then the less confident one can be about estimating where the
    vessel
    > is on the celestial LOP.
    >
    
    
    

       
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