[Proj] Winkel Tripel Problems

[Mikael Rittri]

Lars wrote:

> ... I wonder why Winkel Tripel is not supported.

Probably because Proj.4 supports only the forward direction
(from Long/Lat to projected coordinates).

>proj +proj=wintri -I
Rel. 4.8.0, 6 March 2012
<proj>:
inverse projection not available
program abnormally terminated

You might think that you only wanted the forward direction, but
for many purposes both directions are needed. I don't know about
QGIS, but maybe they decided to ignore Winkel Tripel completely. 

Some years ago, Oscar van Vlijmen gave a link to a paper that
that described how to invert Winkel Tripel.

   http://lists.maptools.org/pipermail/proj/2007-May/002964.html

Another version of the paper was published in the CaGIS journal,
see 

   http://lists.maptools.org/pipermail/proj/2008-September/003799.html

Best regards,

Mikael Rittri
Carmenta
Sweden
http://www.carmenta.com

-----Original Message-----
From: proj-bounces at lists.maptools.org [mailto:proj-bounces at lists.maptools.org] On Behalf Of Lars Pennig
Sent: den 9 maj 2012 16:19
To: proj at lists.maptools.org
Subject: [Proj] Winkel Tripel Problems

Hi all,

since I'm working with QGIS (which relies on proj) I wonder why Winkel
Tripel is not supported. I understand that Winkel Tripel is integrated
in proj (+proj=wintri) but that seems not to work. For Example, defining
a user projection with +proj=wintri within qgis and then trying to
project (on the fly) a dataset of epsg:4326 (plate carree) to this
projection fails. Instead qgis shows the existing dataset in epsg:4326.

Anyone out there with a solution?

Thanks in advance, Lars
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