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    Re: Direct methods
    From: George Huxtable
    Date: 2007 Nov 3, 20:25 -0000

    I give up. I have tried to send the attached file in .rtf (rich text
    format), with the idea that it would be available to anyone irrespective of
    whether they had proprietary Microsoft Word software on board. If I post
    that file directly to myself it comes back OK. In the dying days of Nav-l, I
    posted it there, and it came back OK. But for some reason, .rtf files sent
    to navlist get corrupted somewhere along their round trip. Anyone know why?
    
    Anyway, let's try it this time with .doc format.
    
    The text of my 1 Nov message is copied, once again, below.
    
    ======================
    
    d walden's first posting with its attachment came over successfully to me.
    It may present problems to anyone that doesn't have Excel aboard as his
    spreadsheet.
    
    
    He wrote-
    
    |    It is of course possible, as has been pointed out, to calculate the
    latitude and longitude of the points of intersection of two circles of
    position directly with neither an estimated nor an assumed position.  Nor in
    fact are altitudes and intercepts or any plotting needed.  The intersection
    of cones method, described by Frank in the discussion of latitude by lunars,
    and shown in a previously posted FORTRAN and Maxima example can be used.  A
    few minor changes to the programs posted are needed.
    |
    |  The problem is, in fact, slightly easier.  It can be done with
    intersecting planes.  The attached little spread sheet is an example of how.
    One enters with the altitude, declination, and GHA of two bodies.  Out come
    the latitudes and longitudes of the two intersection points.  If you have
    three bodies, pick a different pair, and two of the points should wind up
    quite close.  There you are.
    |
    |  Seems to be working for me, but no guarantees.
    
    ===================
    
    For completeness, if nothing else, I resend an attachment which originally
    went out to the old Nav-L list on 12 June 06, under the threadname
    "positions from crossing two circles". That provided a routine, written in
    Bastard-Basic for a Casio pocket-calculator, to determine the two possible
    positions that result from crossing two observations. It also explains how
    the thing works.
    
    I remember that Andres followed it up with a posting in which he had
    converted it to a program written in C.
    
    George.
    
    contact George Huxtable at george---.u-net.com
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    
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    File: 103758.intersecting-circles.doc
       
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