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    Re: That darned old cocked hat
    From: Tom Sult
    Date: 2010 Dec 10, 08:56 -0600
    I agree. I am a minor math-o-phile and CelNav user. If you are making landfall or in hazardous waters CelNav is a strategic tool not tactical. We use CelNav to navigate well clear of bad thing not to tiptoe through them. We use other methods to do the close tactical work. Again like mark I eyebal,l a good chart, compus and not hitting the stuff we see out the window. 
    But I love the elegance of the math. And the "simplicity"..."a good ship and a star to steer her  by". Although I would also like a GPS or two. (my plane has three). 

    Thomas A. Sult, MD
    Sent from iPhone

    On Dec 10, 2010, at 2:34, Andres Ruiz <aruiz@orona.es> wrote:

    ---Peter wrote:

    Systemic error can be dealt with by bisecting each angle formed by intersecting position lines.


    If a triangle, and azimuths with a spread of less than 180 degrees, then the fix will be outside the triangle.  The probability is 100%.

    With an azimuth spread greater than 180 degrees, then the fix will be at the centre of the triangle.  The probability is, again, 100%.


    I think there is some misunderstanding about bisector method:

    ·         One is bisecting the angle of the triangle

    ·         an another is to use the bisector of the azimuths of each pair of LoP. Has the important property
    that is free of systematic errors.






    ---Tom wrote:

    I think it would be interesting to see the results of various methods.  But I must confess, I use "Mark I eyeball" to estimate best fit.



    For the example CY3 in my previous e-mail the solution by the bisector of the azimuth is the same as in LS:





    I am agree with Tom; one thing is the mathematical basis, very interesting of course, and another is the real world, where in practical navigation I take for the fix in a cooked hat, not a point, but a circle with a radius based in my experience and felling of the circumstances, is the blue, not the coast, where piloting techniques must be employed.


    Andrés Ruiz
    Navigational Algorithms


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