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Dear developers,<br>
<br>
I'm not sure who is responsible for the problem that I'm going to
describe. This problem is very serious for me and for a lot of
other people who are trying to use Open Source GIS software (especially
in the Czech republic).<br>
<br>
1.<br>
Library PROJ.4 has (next to the "<b>proj</b>" program) also program "<b>cs2cs</b>"
("<i>The new <b>cs2cs</b> program performs a similar function
to the <b>proj</b> program, but transforming from any one coordinate
system
to another. The new <b>pj_transform()</b> is used to access the
extended
coordinate system to coordinate system transformation with datum
shifting</i>."). This program is a great thing, but unfortunately it
looks like
just a few GIS programs are using <b>cs2cs</b> instead of the <b>proj</b>
program. For example, there is no problem with the coordinate
transformation used in the PostGIS
(which probably uses <b>cs2cs</b>). However, the utilities of the <b>GDAL</b>
and the <b>OGR</b>
library, which are a base for a lot of other applications (MapServer,
QGIS and so on), are
probably
using the <b>proj</b> program for coordinate transformations. This
fact makes quite a big position shift
after the coordinate transformation between coordinate systems based on
diferent ellipsoids (<b>proj</b> program cannot make datum shifting).
Finally, it is not possible to transform data correctly or to display
more
datasets based on different ellipsoids in a detailed view by the way of
on-the-fly projection (the shift between elipsoids is often bigger than
100 meters).<br>
<br>
Does somebody have any ideas? Is possible to make changes in the GDAL
and OGR source
codes and use the <b>cs2cs</b> instead of the <b>proj</b> program?<br>
<br>
<br>
2.<br>
(probably to Frank Warmerdam)<br>
In the Czech Republic we are using a strange coordinate
system known as "krovak" (S-JTSK). This system has a strange axis
orientation that
is very hard to apply in the computer world, so nobody is using this
axis
orientation in GIS. Instead everybody is using switched axis ( X = -y,
Y = -x
). If somebody would like to use proj.4 library, they have to use a
patch
for proj.4 library ( <a class="moz-txt-link-freetext"
href="http://mpa.itc.it/radim/jtsk/PJ_krovak.c.patch">http://mpa.itc.it/radim/jtsk/PJ_krovak.c.patch</a>
).
For a lot of people it is very hard to apply this patch because they
are just users who want to use an open source GIS software that uses
proj.4 library. I can remember that this problem was discused by Radim
Blazek and Frank Warmerdam but no successfull result were found... I
think.<br>
<br>
Is there any possibility to include this patch into an official version
of
proj.4 library? Or in the case that you want to keep this a
"well-defined" krovak system, is
possible to make a new definition of krovak with a different EPSG code
(and keep the old one (esri:102065) in case there is an individual
person who is using
this definition)?<br>
<br>
<br>
These two problems are major for a lot of people that I know and these
are two of
the main reasons why they are not going to use open source GIS software
(and that is pity of course)...<br>
<br>
<br>
Thank you for feedback.<br>
<br>
Best regards,<br>
Antonin Orlik<br>
<br>
<pre class="moz-signature" cols="72">--
Ing. Antonin Orlik
Institute of Geoinformatics
VSB-Technical University of Ostrava
17.listopadu 15/2172
708 33 Ostrava-Poruba
E-mail: <a class="moz-txt-link-abbreviated"
href="mailto:antonin.orlik.hgf@vsb.cz">antonin.orlik.hgf@vsb.cz</a>
Office: J 327
Tel: +420 59 732 3337
Mobile: +420 604 333 744
ICQ: 54928537</pre>
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