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    Re: Ellipse of Confidence in position finding
    From: Bill Lionheart
    Date: 2019 Mar 18, 07:22 +0000

    Robin,
    Are there published  suggestions related to the distance between
    assumed position and GP of the celestial body?  Obviously if you are
    close enough for the GP to be on your plotting sheet you can draw a
    circle of position.
    Bill
    
    On Mon, 18 Mar 2019 at 00:33, Robin Stuart  wrote:
    >
    > Geoffrey,
    >
    >         The authors of the Nautical Almanac believe this to be 20 nautical 
    miles. The method they describe in the section Position from intercept and 
    azimuth by calculation on p.282 (2010) requires that the procedure be 
    iterated until the initial and final estimates of position are within 20 
    miles of each other.
    >
    > “If d exceeds about 20 nautical miles set LF = LI, BF = BI and repeat until 
    d, the distance between the position at the previous estimate and the 
    improved estimate, is less that 20 nautical miles”
    >
    > The equations being used in the least squares calculation of position are 
    exact in within the straight LoP approximation. The iteration is required to 
    ensure that the approximation is a good one and that curvature of the LoP’s 
    can be neglected,
    >
    > Robin Stuart
    >
    > View and reply to this message
    

       
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