[Proj] Re: Discovery: libproj4 stmerc = French Gauss-Laborde projection

[strebe at aol.com]

Hm. I didn't know about that web page. Obviously it's wrong -- for some 
reason "p" appears in several different roles. I tend to think that's 
an error in conversion to a web page. (I see that the entire blurb is a 
single graphic, not HTML mark-up.) Certainly he's been pedantic and 
precise in all his communications with me.

The p/2 exponent should read (e/2), where e is the eccentricity.

Use some other variable (perhaps p') in place of p in "Then, the 
complex variable tan (p/2) can be obtained..." and "...yields the 
argument p..."

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: Wed, 14 Jun 2006 11:42:40 -0400
Subject:  Re: [Proj] Re: Discovery: libproj4 stmerc = French 
Gauss-Laborde   projection

   On Wednesday 14 June 2006 1:12 am, Strebe at aol.com wrote:
> You might contact Dr. David E. Wallis. He devised a much simpler 
method
> than Dozier's. I've implemented it for the full-ellipsoid. You can 
see a
> plot of an earth-like ellipsoid here:
>
> 
http://mapthematics.com/Projection%20Images/Cylindrical/Transverse%20Merc
at
>or. GIF
>
> The method works for arbitrary eccentricities. Contact me privately if
> you're interested. Since it is Dr. Wallis's invention, I'll put you in
> contact with him.

Dr. Wells has a web page relating to the projection:

http://www.wallisphd.com/mercator.htm

that a Google search on his name will return.  Found this site several 
years
ago during a previous discussion about tmerc.  To me, the web page 
appears
unchanged and the "Publication Pending" notice at the top is certainly 
taking
a long time.

I should post him a letter for further information and follow up with a 
phone
call if no response.

The description of the equation present does not make much sense unless 
what
looks like p in the tan term is not the p described as colatitude.  
Again,
the first line says p,lambda is the colatitude and longitude yet the
description following the formula talks about a p for the Elliptic 
Integral
of the second kind.

I must be missing something.

--
Jerry and the low-riders: Daisy Mae and Joshua
"Cogito cogito ergo cogito sum"
   Ambrose Bierce, The Devil's Dictionary
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