# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Direct methods
From: George Huxtable
Date: 2007 Nov 1, 23:53 -0000

```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

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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```

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