[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.

-- 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.




-----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 
> 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 
> "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 
with the North Polar Stereographic Projection of the spheroid along the
principal meridian is put into a Newton-Raphson iteration that solves 
the tangent of one half the parametric colatitude, generalized to the
complex plane. ..."

There is documentation available ($) and Fortran software ($). Export 
out of
the USA is forbidden.
"The program was developed in 1989."

Texts between "" are quotes from web pages found at the Open Channel

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