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    Re: Irregular Quadrilateral Center
    From: Peter Hakel
    Date: 2015 Feb 6, 04:05 +0000
    These calculations can be performed with Excel:


    They can also account for vessel motion. The method and the problem preset in this spreadsheet were taken from pp. 282-283 of the Nautical Almanac, 2010 Commercial Edition.

    Peter Hakel

    From: Robin Stuart <NoReply_Stuart@fer3.com>
    To: pmh099@yahoo.com
    Sent: Thursday, February 5, 2015 6:31 AM
    Subject: [NavList] Re: Irregular Quadrilateral Center

    The procedure for finding the centre of a quadrilateral or other figure is described in the Nautical Almanac. I don't have the page number with me but the formulas involve sums of sines and cosines of azimuths. The formulas are derived by a least squares fit to the observations. If you apply the formulas to 3 observations you'll get the symmedian point of the cocked hat that has been discussed here extensively. The formulas in the NA assume that any constant offset (such as an unknown Index Error) is zero. It is a fairly easy matter to extend the method to perform the least squares fit incorporating an unknown constant and actually produce a value for it.
    Robin Stuart

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