[Proj] Re: Discovery: libproj4 stmerc = French Gauss-Laborde
strebe at aol.com
strebe at aol.com
Mon Jun 19 12:59:59 EDT 2006
I doubt the Open Channel Foundation source code has anything to do with
Wallis unless the program was written by someone else he communicated
with without his knowledge. Dr. Wallis has never tried to sell me
anything; never mentioned the existence of commercial source code; and
has communicated with me about his own implementation, including
algorithmic subtleties and requests for independent confirmation of
accuracy. He also considers the method to be "obvious" and not worth
publication on its own. On the other hand, either he believes he
originated the method, or else wanted me to believe he did.
I can't say whether the product mentioned before came first, or whether
Dr. Wallis's method came first. I made Dr. Wallis's acquaintance in
1996, and I know he had written his implementation years before that,
though I don't know how many. I'll contact him about the Open Channel
Foundation program.
$61 for source code and documentation seems modest enough, but the
inane export restrictions won't help Mr. van Vlijmen. While I will not
supply source code, I'm happy to answer specific questions about
implementing the method.
Regards,
-- daan Strebe
-----Original Message-----
From: Gerald I. Evenden <gerald.evenden at verizon.net>
To: PROJ.4 and general Projections Discussions <proj at lists.maptools.org>
Sent: Mon, 19 Jun 2006 10:42:51 -0400
Subject: Re: [Proj] Discovery: libproj4 stmerc = French Gauss-Laborde
...
Interesting: I could not find an author associated with the
product--maybe it is Dr. Wallis.
-----
and
-----
-----Original Message-----
From: Oscar van Vlijmen <ovv at hetnet.nl>
To: PROJ.4 and general Projections Discussions <proj at lists.maptools.org>
Sent: Mon, 19 Jun 2006 14:09:30 +0200
Subject: Re: [Proj] Discovery: libproj4 stmerc = French Gauss-Laborde
> From: Strebe-aol.com
> The "trick" is this: Wallis uses the polar stereographic because it's
the
> simplest way to get a conformal mapping to the plane. Once the
ellipsoid is
> mapped, he treats the plane as the complex plane and looks for a
complex
> "co-latitude" which can be used with the polar stereographic, but
this time
> treating the polar stereographic as function of a complex variable.
Now where have I seen this again?
Ah yes:
"Transverse Mercator Map Projection of the Spheroid Using
Transformation of
the Elliptic Integral software (NPO-18086)."
"... Using the colatitude (complement of latitude) and the longitude
(departure), the initial step is to map the point to the North Polar
Stereographic Projection. The closed-form, analytic function that
coincides
with the North Polar Stereographic Projection of the spheroid along the
principal meridian is put into a Newton-Raphson iteration that solves
for
the tangent of one half the parametric colatitude, generalized to the
complex plane. ..."
Etcetera.
There is documentation available ($) and Fortran software ($). Export
out of
the USA is forbidden.
"The program was developed in 1989."
<http://www.openchannelfoundation.org/projects/Transverse_Mercator_Map_Pr
oje
c/>
Texts between "" are quotes from web pages found at the Open Channel
Foundation.
_______________________________________________
Proj mailing list
Proj at lists.maptools.org
http://lists.maptools.org/mailman/listinfo/proj
________________________________________________________________________
Check out AOL.com today. Breaking news, video search, pictures, email
and IM. All on demand. Always Free.
More information about the Proj
mailing list