NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Irregular Quadrilateral Center
From: Peter Hakel
Date: 2015 Feb 6, 04:05 +0000
From: Peter Hakel
Date: 2015 Feb 6, 04:05 +0000
These calculations can be performed with Excel:
http://www.navigation-spreadsheets.com/lops.html#many_body_fix
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
http://www.navigation-spreadsheets.com/lops.html#many_body_fix
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
Greg,
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
