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<p style="margin-bottom: 0cm;">Dear developpers and users of QGIS </p>
<p style="margin-bottom: 0cm;">First of all i want to thank the
developers of Qgis for this excellent software that i follow since
the version 0.9 Now the number of my colleagues using QGIS is
increasing. Itr is very usefull for our experimental work in the
field (with soil mapping and localisation and agronomical trials )
and we also start now to use Qgis with a differential gps, in order
to localize very precisely some new samplings and field trials and
indicate them in previous maps.</p>
<p style="margin-bottom: 0cm;">Therefore for our work, the QGIS
version 1.7.4 with "on the fly" projection of vectors and
rasters is very interesting. </p>
<p style="margin-bottom: 0cm;">Unfortunately I have a now a quite
tricky problem with Qgis 1.7.4 for Debian Squeeze (obtained from the
Qgis repository <a class="moz-txt-link-freetext" href="http://qgis.org/debian/">http://qgis.org/debian/</a>) . And, following my tests this
problem does not occur with some other OS and QGIS 1.7.4 (namely
Windows and Ubuntu) </p>
<p style="margin-bottom: 0cm;">In Debian Squeeze with the version 1.7.4
of QGIS, whatever i do, when i try"on the fly projection" (of course
with on "the
fly reprojection" activated ) i have systematically <i><b>a shift of
about 50 meters</b></i> between my layers in "lambert II etendu"
and the layers two other projections (Lambert 93 and RGFCC43) .... </p>
<p style="margin-bottom: 0cm;">I give some details of my trials in the
Annex below<br>
</p>
<br>
So .. this is a bit a headache for me …
i sincerely think that the problem comes from the Debian squeeze
version .. probably my configuration, but may be a more general problem
with Debian squeeze and QGIS 1.7.4
<p style="margin-bottom: 0cm;">I would want to use QGIS 1.7.4 with
Debian stable (Squeeze) and to have good "on the fly
projections" and good reprojections for my lcc layers … but
for the moment is seems difficult … </p>
<p style="margin-bottom: 0cm;">So thank you in advance if you could
give me some help</p>
<p style="margin-bottom: 0cm;">Kind regards</p>
<p style="margin-bottom: 0cm;"><br>
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<br>
</p>
<p style="margin-bottom: 0cm;">ANNEX about the tests that i did<br>
</p>
<p style="margin-bottom: 0cm;">I first tried to verify that i did not
made mistake with my layers … <br>
some of my layers in
lambert II etendu came from reprojections of "old" layers
in lambert zone III and i wondererd if i made good reprojections . <br>
But such a mistake would not be logical because these
reprojected layers are very well overlaid in QGIS with orthophotos in
lambert
II etendu, and also i can find very precisely the localisation of my
observations in geospatial websites if i convert the localisation
provided by my layers in lambert II etendu in geographical
coordinates. </p>
<p style="margin-bottom: 0cm;">i also tried
in Debian squeeze to find a way to obtain a good overlaying several
combinations, Then i also observed
that when i make a real reprojection (not on the fly) with my vector
layers in RGFCC43 to lambert II etendu (with softwares such
as IGNMAP) all the layers including the layers in CC43 were perfecty
overlaid in a project in
lambert II etendu !! This indicated to me that my layers should
be definitively ok and should overlay. .. </p>
<p style="margin-bottom: 0cm;">So i finally was convinced that all my
layers were correct and should overlay perfecly !! .. and that
this problem could come from somewhere else. </p>
<p style="margin-bottom: 0cm;">Then, "just by chance" i had
to try QGIS 1.7.4 for Windows and i tried with exactly the same
layers that i have : several layers in lambert II étendu, one
vector (dgps datat) in CC43 and two rasters in lambert 93 (just a
copy from the files udes in Debian, of course same projections , and
same parameters in Qgis with "on the fly reprojection activated)
) And .. Bingo !! this shift of 50 m disappeared immediately
with Qgis 1.7.4 for Windows. </p>
<p style="margin-bottom: 0cm;">Well, i then tested QGIS 1.7.4 for
Gnu/Linux Ubuntu distribution LTS Lucid Lynx and second Bingo !!
. In this two cases all my layers were immediately and perfectly
overlaid together !!.</p>
<p style="margin-bottom: 0cm;">So .... this 50 m shift seems to be
connected with the Debian version … But i still want to use
Debian, that i use daily !! (:-) </p>
<p style="margin-bottom: 0cm;">… Thereafter i tried to compare the
versions of QGIS 1.7.4 in the three OS </p>
<p style="margin-bottom: 0cm;">As indicated in the message "about"
i have this specifications <br>
</p>
<p style="margin-bottom: 0cm;">Qgis 1.7.4 for Debian squeeze is
compiled from the version "exported" of the code<br>
and is using :<br>
GDAL/OGR version 1.6.3<br>
Version de QWT : 5.2.0.<br>
is compiled with Qt 4.6.3 and run with
Qt 4.6.3 </p>
<p style="margin-bottom: 0cm;">Qgis 1.74 for lucid Lynx LTD (which
does not have also this 50 m shift) is compiled from the version
"exported" of the code<br>
and is using :<br>
GDAL/OGR version 1.8 .0<br>
Version de QWT : 5.2.0.<br>
is compiled with Qt 4.6.2 and run with
Qt 4.6.2 </p>
<p style="margin-bottom: 0cm;"> </p>
<p style="margin-bottom: 0cm;">Qgis 1.7.4 for windows (which does not
have this 50 m shift") is compiled from version 411aff6 of the
code<br>
and is using :<br>
GDAL/OGR version 1.8.1<br>
Version de QWT : 5.2.1.<br>
is compiled with Qt 4.7.1 and run with
Qt 4.7.1</p>
<p style="margin-bottom: 0cm;">From this comparison I supposed that my
problem could be linked with the version of GDAL/OGR which is a bit
older in the Debian Squeeze. Then i uninstalled Qgis 1.7.4 in Debian
(with purge), also in uninstalled all the libgdal and I reinstalled
QGIS 1.7.4 after having added the gfoss repository to obtain
libgdal1-1.7.0. Unfortunately, even with libgdal1-1.7.0 installed in
Debian, QGIS 1.7.4 still says that it is using GDAL/OGR 1.6.3..
Also if i try to just uninstall libgdal1-1.6.0 (which is named
version 1.6.3-4+b1 (stable)) the synaptic package manager says that
it would uninstall Qgis.... </p>
<p style="margin-bottom: 0cm;">
------------------------------------------------------------------------------------------------</p>
<p style="margin-bottom: 0cm;">By the way i also observed a strange
behaviour in the metadata for the Debian version<br>
(i'm not sure that this is connected with the
previous one, but it would not be impossible)</p>
<p style="margin-bottom: 0cm;"><br>
</p>
<p style="margin-bottom: 0cm;">In my three Operating systems, the
proj4 definition of the projection Lambert II etendu IGNF:LAMBE ID :
10090 indicates the use of a nadgrid ntf_rgf93 like this :<br>
+proj=lcc +nadgrids=ntf_r93.gsb,null
+a=6378249.2000 +rf=293.4660210000000 +pm=2.337229167
+lat_0=46.800000000 +lon_0=0.000000000 +k_0=0.99987742
+lat_1=46.800000000 +x_0=600000.000 +y_0=2200000.000 +units=m
+no_defs </p>
<br>
<p style="margin-bottom: 0cm;">However in Debian Squeeze version of
Qgis 1.7.4 when i "right click" on a layer in "Lambert
II etendu" to obtain the properties and the medatata about the
SCR the +nadgrids=ntf_r93.gsb,null simply disappears in the medata ,
and i just obtain this :<br>
+proj=lcc +lat_1=46.8 +lat_0=46.8
+lon_0=0 +k_0=0.99987742 +x_0=600000 +y_0=2200000 +a=6378249.2
+b=6356514.999978254 +pm=2.337229167 +units=m +no_defs </p>
<p style="margin-bottom: 0cm;">(by the way i think that there is no
problem with
the b instead of rf, it is ok, as b = a*(1 - 1/rf)) The only problem
seems to be with +nadgrids=ntf_r93.gsb,null which have disappeared in
the metadata provided <br>
</p>
<p style="margin-bottom: 0cm;"> </p>
<p style="margin-bottom: 0cm;">Moreover, in the other OS (Ubuntu
Lucid lynx and Windows) i still have the +nadgrids=ntf_r93.gsb,null
in the metadata. I obtain this by a right click on the layer and
going the metadatya :<br>
+proj=lcc +lat_1=46.8 +lat_0=46.8
+lon_0=0 +k_0=0.99987742 +x_0=600000 +y_0=2200000 +a=6378249.2
+b=6356514.999978254 +nadgrids=ntf_r93.gsb,null +pm=2.337229167
+units=m +no_defs </p>
<p style="margin-bottom: 0cm;">(by the way I also verified that i have
the same file ntf_rg83.gsb in usr/share/proj in Ubuntu and in Debian
versions .. it is ok i have the same file (same size, same md5sum)... <br>
</p>
<p style="margin-bottom: 0cm;">finally for the proj, proj-bin and
proj-data
package i have 4.7.0-1 in, Debian squeeze and 4.7.0-2 in Ubuntu Lucid
Lynx (i'm note sure also if this is important or not) </p>
<br>
<p style="margin-bottom: 0cm;"><br>
</p>
<p style="margin-bottom: 0cm;"><br>
</p>
<p style="margin-bottom: 0cm;"> </p>
<p style="margin-bottom: 0cm;"><br>
</p>
<p style="margin-bottom: 0cm;"> </p>
<p style="margin-bottom: 0cm;"> </p>
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<p style="margin-bottom: 0cm;"><font size="2">_______________________________________________________________________________________</font></p>
<p style="margin-bottom: 0cm;"><font color="#008000"><font size="2"><b>Didier
B</b><b>lavet</b> </font></font>
</p>
<p style="margin-bottom: 0cm;"><font color="#000000"><font size="2">Institut
de
Recherche pour le Développement - IRD (<font color="#0000ff"><a class="moz-txt-link-freetext" href="http://www.ird.fr">http://www.ird.fr</a></font>)
</font></font></p>
<p style="margin-bottom: 0cm;"><font color="#000000"><font size="2">UMR
Eco&Sols - Ecologie Fonctionnelle & Biogéochimie des Sols &
Agroécosystèmes </font></font>
</p>
<p style="margin-bottom: 0cm;"><font color="#000000"><font size="2">(Montpellier
SupAgro-CIRAD-INRA-IRD)
(<font color="#0000ff"><a class="moz-txt-link-freetext" href="http://www.montpellier.inra.fr/ecosols">http://www.montpellier.inra.fr/ecosols</a></font><span
style="font-style: normal;">)</span></font></font></p>
<p style="margin-bottom: 0cm;"><font color="#000000"><font size="2">Bâtiment
12,
2 place Viala, F-34060 Montpellier Cedex 2 , France </font></font>
</p>
<p style="margin-bottom: 0cm;"><font color="#000000"><font size="2">Tel
bureau : +33 (0)4 99 61 21 33 </font></font>
</p>
<p style="margin-bottom: 0cm;"><font color="#000000"><font size="2">Secrétariat
:
+33 (0)4 99 61 21 01 / Fax : +33 (0)4 99 61 21 19 </font></font>
</p>
<p style="margin-bottom: 0cm;"><font color="#000000"><font size="2">Courriel
:
<font color="#0000ff"><a class="moz-txt-link-abbreviated" href="mailto:didier.blavet@ird.fr">didier.blavet@ird.fr</a></font> </font></font>
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