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    Re: Advance LOP of High Speed Vessel
    From: Peter Hakel
    Date: 2012 Nov 9, 03:34 -0800
    Bruce,

    If you are interested in performing computations that mirror the graphical procedures, you can take a look at:

    http://www.navigation-spreadsheets.com/dead_reckoning.html#running_fix
    http://www.navigation-spreadsheets.com/lops.html#many_body_fix


    Peter Hakel


    From: Antoine Couëtte <antoine.m.couette{at}club-internet.fr>
    To: NavList@fer3.com
    Sent: Thursday, November 8, 2012 10:56 PM
    Subject: [NavList] Re: Advance LOP of High Speed Vessel

    RE: [NavList] Re: Advance LOP of High Speed Vessel
    From: Greg Rudzinski
    Date: 8 Nov 2012 18:35
    Bruce,
    There are two ways which I use to advance lines of position.
    1. Advance the assumed position along the vessel heading using time, speed and distance tables or a pocket calculator. From the advance A.P. plot the azimuth and intercept.
    2. Advance the line of position from the course track intersection along the track line to the desired DR position.
    Greg Rudzinski

    *******

    Hello Bruce,
    The matter of advancing LOP's (which are circles on a sphere and more complex figures on an ellipsoid) has been subject to intense debates here. Most rigorous mathematical treatments exist and have been published. They are already complicated on a sphere with a moving vessel when speed and course do not change, and could become (extremely) complex in case of Speed and/or courses changes. On an ellipsoid, they even become more difficult to rigorously tackle.
    Are all these mathematical computations really necessary ???
    In other words, are such mathematical tedious computations the only and unique way/path to get to the "best" result you can reasonably expect given your seaborne/airborne environment with all its uncertainties about sea currents or winds ????
    In real life, in addition to its inherent inaccuracies the "overall quality" of any LOP's degrade and will degrade when carried out forward or backwards in time, mainly due to uncertainties about Dead Reckoning. You will the see that in real life such Dead Reckoning uncertainties (far) outweigh/exceed the subtle and tedious mathematical treatments mentioned here-above.
    After extended simulation and careful considerations I have settled for "Solution 1" described hereabove by Greg , i.e. :
    "Advance the assumed position along the vessel heading using time, speed and distance tables or a pocket calculator. From the advance A.P. plot the azimuth and intercept."
    This method will work whatever the craft speed (including A/C at 300 kt). It is within (easy and reasonable) reach of Tables or Calculators even if successive changes of course and/or speed and it can also easily accommodate Sea Currents or (Airborne) Wind if you use vectors in your computations.
    Yes, to solve that matter I definitely advocate such "Solution 1" described by Greg.
    Best Regards to all.
    Kermit
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