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yes, there are definite issues with the list

I'm looking into the problems as I get time.









On 6/12/06, George Huxtable  wrote:
> An interesting posting in the thread  "Position from crossing two
> circles : was [NAV-L] Reality check"
>
> was sent: Thursday, June 08, 2006 7:48 AM, by Andres Ruiz.
>
> It included, within the text of the message I received, a diagram of a
> sphere with two intersecting circles drawn on it. That in itself is
> unusual for Nav-l messages, which are usually sent, as requested, in
> text-only mode; but I am not opening that question. Presumably the
> message must have been sent in HTML; but if a plain-text version
> accompanied it, perhaps I would be unaware.
>
> What interests me more is that following a reply to that message,
> Frank Reed wrote, on that same day,
>
> "I didn't receive this message  and there's no evidence of it in the
> irbs
> archive that I can find --possibly it  was a private message-- but I
> would be
> interested in receiving a copy. Could  someone forward a copy to me?
> Thanks."
>
> This seems to me to be worth following-up, for any light it may throw
> on the question of missing messages, which seem to be still plaguing
> the list.
>
> I looked into responding to Frank's request, but when I tried to
> forward a copy, it had that diagram stripped out, perhaps because my
> own emailer program is set to send in plain-text only. So I gave up on
> that. Later, Frank informed us that a copy had been forwarded to him
> from another member, so all was well. I wonder if that forwarded copy
> included the original diagram.
>
> On request, Andres resent his original posting on 9 June. In fact,
> there were 3 resends on that day, so altogether 4 such postings were
> sent altogether. There may possibly have been more, of course, but
> those were what reached me. All included that diagram. There were, in
> addition, shorter postings from him around that time on that same
> topic, which do not concern me.
>
> I wonder how many (if any) copies of that original Andes Ruiz posting
> arrived in Frank's mailbox, not counting any forwarded copies that
> arrived from elsewhere. Did they include that diagram? From those that
> keep an eye on the i-DEADLINK-com archive, how many copies of Andres'
> original posting appeared? Did they include the diagram? Did other
> members fail to receive all four copies of that message, with its
> diagram? If less than four, how many?
>
> Only by collating such evidence do we have any hope of discovering
> what's going wrong.
>
> George.
>
> contact George Huxtable at george@huxtable.u-net.com
> or at +44 1865 820222 (from UK, 01865 820222)
> or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
>
>
>
>
>
>
>
> Geoge, the method is not impossible for n observations or running fix.
>
> Mike, here you have the math for a fix from two circles of position
> (COP)
>
> Enjoy.
>
>
>
> 1. Position from two circles of equal altitude
>
>
>
> The equation of the plane containing a COP in rectangular coordinates
> is:  ax+by+cz-p = 0
>
> For the two bodies you have two equations, two planes intersect in a
> line.
>
> The two possible solutions for the observer's position, P and P', are
> the intersections of that line with the unit sphere  x2+y2+z2 = 1
>
>
>
> the math, (in C++):
>
>
>
> /*
>
>             File: fix2circulosAltura.cpp
>
>
>
>             This file contains proprietary information of Andr?s Ruiz
> Gonzalez
>
>             Open source
>
>
>
>             Andr?s Ruiz. San Sebastian - Donostia. Gipuzkoa
>
>             Copyright (c) 2006
>
> */
>
>
>
> #include "stdafx.h"
>
> #include 
>
> #include "..\LSfix\mathlib.hpp"
>
>
>
>
>
> double raiz1 = 0;
>
> double raiz2 = 0;
>
>
>
>
>
> void Ecuacion2grado( double a, double b, double c )
>
> {
>
>  double f = b*b-4.0*a*c;
>
>  raiz1 = (-b+sqrt(f))/2.0/a;
>
>  raiz2 = (-b-sqrt(f))/2.0/a;
>
> }
>
>
>
>
>
> // Inputs
>
> double GHA1, dec1, HO1;
>
> double GHA2, dec2, HO2;
>
> // Outputs
>
> double B1, L1;
>
> double B2, L2;
>
>
>
> void PosicionPorInterseccion2circulosAltura()
>
> {
>
>  double a1 = COS(360.0-GHA1) * COS(dec1);
>
>  double b1 = SIN(360.0-GHA1) * COS(dec1);
>
>  double c1 = SIN(dec1);
>
>  double p1 = COS(90.0-HO1);
>
>
>
>  double a2 = COS(360.0-GHA2) * COS(dec2);
>
>  double b2 = SIN(360.0-GHA2) * COS(dec2);
>
>  double c2 = SIN(dec2);
>
>  double p2 = COS(90.0-HO2);
>
>
>
>  double A = a1*b2 - a2*b1;
>
>  double B = b2*c1 - b1*c2;
>
>  double C = b2*p1 - b1*p2;
>
>  double D = a1*c2 - a2*c1;
>
>  double E = b1*c2 - b2*c1;
>
>  double F = c2*p1 - c1*p2;
>
>
>
>  double K = F/E;
>
>  double J = D/E;
>
>  double G = C/B;
>
>  double H = A/B;
>
>
>
>  double alpha = 1.0+J*J+H*H;
>
>  double beta  = -2.0*K*J-2.0*G*H;
>
>  double gamma = K*K+G*G-1.0;
>
>
>
>  Ecuacion2grado( alpha, beta, gamma );
>
>
>
>  double x1 = raiz1;
>
>  double y1 = K-J*x1;
>
>  double z1 = G-H*x1;
>
>
>
>  double x2 = raiz2;
>
>  double y2 = K-J*x2;
>
>  double z2 = G-H*x2;
>
>
>
>  B1 = ATAN( z1/sqrt(x1*x1+y1*y1) );
>
>  L1 = ATAN( y1/x1 );
>
>
>
>  B2 = ATAN( z2/sqrt(x2*x2+y2*y2) );
>
>  L2 = ATAN( y2/x2 );
>
> }
>
>
>
> void CAstroLSDlg::OnCalcular()
>
> {
>
>  UpdateData();
>
> /*
>
>  GHA1 = 347.78;
>
>  dec1 = -16.72;
>
>  HO1 = 19.55;
>
>
>
>  GHA2 = 334.23;
>
>  dec2 = 5.22;
>
>  HO2 = 28.5;
>
> */
>
>
>
>  GHA1 = 20.06;
>
>  dec1 = 16.52;
>
>  HO1  = 90-26.87;
>
>
>
>  GHA2 = 332.71;
>
>  dec2 = 28.02;
>
>  HO2  = 90-48.02;
>
>
>
>  PosicionPorInterseccion2circulosAltura();
>
>
>
>  CString tmp = "";
>
>  tmp.Format( "1(%.4lf ?, %.4lf ?)  2(%.4lf ?, %.4lf ?)", B1, L1, B2,
> L2 );
>
>  m_output = tmp;
>
>
>
>  UpdateData( FALSE );
>
> }
>
>
>
>
>
> 2. Position from n circles of equal altitude
>
> Here the problem is there are a lot of crossings between the circles.
> Metcalf & Metcalf, (On the overdetermined celestial fix - Refer to the
> Bibliography section at the link below), developed a method based on
> Lagrange Least-Squares minimization of the equation:
>
> S ( Sin Ho - [ sin Dec  sin Lat + cos Dec  cos Lat cos(GHA+Lon)  ]2 )
>
>
>
> The result is the MPP(Lat, Lon) for n circles of position. No initial
> position is needed. Also support a running fix.
>
>
>
>
>
> MIKE:
>
> What is the C++ application you refer for calculate and plot the COP?,
> where can I found it?
>
> Thanks.
>
>
>
> http://www.geocities.com/CapeCanaveral/Runway/3568/index.html
>
> Andr?s
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> -----Mensaje original-----
>
> De: Navigation Mailing List
> [mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM] En nombre de Michael Dorl
>
> Enviado el: mi?rcoles, 07 de junio de 2006 13:39
>
> Para: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
>
> Asunto: Re: [NAV-L] Position from crossing two circles : was [NAV-L]
> Reality check
>
>
>
> At 06:10 AM 6/7/2006, George Huxtable wrote:
>
>
>
> >I have written a program in bastard-Basic which runs on my 1980s
> >Casio
>
> >programmable calculator (FX 730P or FX 795P), and if anyone is
>
> >interested would be happy to send it or post it up. It would be
> >simple
>
> >to adapt it to another machine. It takes the 6 quantities, dec, GHA,
>
> >and altitude for each of two bodies, and returns two possible
>
> >positions in terms of lat and long, for the user to choose the
>
> >appropriate one. It does not require a DR or AP, and provides an
> >exact
>
> >result without going through an iteration process.
>
> >
>
> >It's not original, in that versions of the method have been described
>
> >previously beforehand. For example, in an article by George Bennett
> >in
>
> >the journal "Navigation"  (which is, I think, the American one) Issue
>
> >no. 4, vol 26, winter 1979/80, titled " General conventions and
>
> >solutions- their use in celestial navigation", and to the book
>
> >"Practical navigation with your calculator", by Gerry Keys, (Stanford
>
> >maritime, 1984), section 11.12. The method has also been described in
>
> >"The K-Z position solution for the double sight", in European Journal
>
> >of Navigation, vol.1 no, 3, December 2003, pages 43-49, but that
>
> >article was bedevilled by printing errors that render it more-or-less
>
> >unintelligible, which were corrected in a later issue. Not to mention
>
> >several serious errors and misunderstandings by the author, which
> >have
>
> >never been acknowldged or corrected in that journal.
>
>
>
> George:
>
>
>
> Do any of these sources spell out the math in detail?  I've searched
> in
>
> vain for a complete algorithm so a long time ago, I sat down and
> worked out
>
> the math.  One of the tricky things is determining what quadrant
> angles lie
>
> in when doing a inverse trig function.  I have a c++ windows
> application
>
> which will find all the equal altitude circle intersections for a set
> of
>
> observations.  It also can plot the equal altitude circles on a world
> map.
>
>
>
> Mike
>

   

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