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-------- Original Message --------
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">Subject:
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<td>Re: [Qgis-developer] Datum Transformation - parameters
for mainland Portugal</td>
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">Date: </th>
<td>Fri, 20 Jun 2014 09:35:00 +0200</td>
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">From: </th>
<td>Marco Hugentobler
<a class="moz-txt-link-rfc2396E" href="mailto:marco.hugentobler@sourcepole.ch"><marco.hugentobler@sourcepole.ch></a></td>
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">To: </th>
<td>Pedro Venâncio <a class="moz-txt-link-rfc2396E" href="mailto:pedrongvenancio@yahoo.com"><pedrongvenancio@yahoo.com></a></td>
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<div class="moz-cite-prefix">Hi Pedro<br>
<br>
Added two ntv2 entries and updated two entries, hope it is
correct now.<br>
<br>
I still feel uncomfortable to delete / update towgs84 entries in
the qgis db only. I'm concerned this will get a mess over time
if there are lots of updates (and the qgis.db is synchronized
during install with the gdal table).<br>
If the updates are very important, I'd suggest the Portuguese
user group to provide a modified copy of srs.db for people to
download.<br>
<br>
<pre wrap="">>However I came across something quite odd. In the Datum Transformation window, automatically arise some strange transformations (red in the image <a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://goo.gl/iIWOuw">http://goo.gl/iIWOuw</a>). These transformations give huge errors, and I do not >understand what they represent.
QGIS reads all possible combinations to get from one datum to the other. Seems to me these towgs84 transformations are all present in the transformation table (though I don't know the geographical crs related to 30004. Is it 4258?)
</pre>
<br>
>Regarding NTv2 grids (<a moz-do-not-send="true"
class="moz-txt-link-freetext" href="http://goo.gl/jDhxJB">http://goo.gl/jDhxJB</a>)
I have another doubt here. On Linux, these files are placed in
/usr/share/proj. On Windows, using the OSGeo4W installer, they
are >placed in ..\OSGeo4W64\share\proj. With QGIS standalone,
they are placed at ..\Program Files\QGIS Valmiera\share\proj.
There is no possibility of copy the grid files,
>automatically during the installation? This will make it
easier for less experienced users. <br>
<br>
Maybe it could be done in the packaging (location is system
dependent and there is not proj function call to get the right
location).<br>
Budling ntv2 files with the application is a frequent request.
We can discus thiss further after the release. Problems I see
are:<br>
- too large install package if lots of files are present <br>
- requires to check every file license<br>
<br>
Problem 2 can easily be solved if a volountear steps up for
maintaining.<br>
<br>
Regards,<br>
Marco<br>
<br>
On 18.06.2014 15:13, Pedro Venâncio wrote:<br>
</div>
<blockquote
cite="mid:1403097219.59323.YahooMailNeo@web122303.mail.ne1.yahoo.com"
type="cite">
<pre wrap="">Hi all,
I have an update to the parameters that are in Datum Transformation for mainland Portugal.
After an analysis of the parameters that are currently inserted in srs.db, I think we should keep only the latest parameters that are provided by the Portuguese Surveying Authority (Directorate-General of the Territory), to avoid confusion among users.
So, we should keep only the transformation parameters of Molodensky, Bursa-Wolf, and two grids NTv2 that are in use here in Portugal, one from the Directorate-General of the Territory, and another from the University of Porto.
I already have the SQL queries with the changes that I suggest:
delete from tbl_datum_transform
where source_crs_code = 4207 or source_crs_code = 4274;
insert into tbl_datum_transform (epsg_nr,coord_op_code,source_crs_code, target_crs_code,coord_op_method_code,p1,p2,p3,p4,p5,p6,p7,remarks,preferred,deprecated,area_of_use_code)
values (30000,100014,4803,4326,9606,-283.088,-70.693,117.445,-1.157,0.059,-0.652,-4.058,'Parâmetros de Transformação de Bursa-Wolf do Datum Lisboa para PT-TM06-ETRS89 (Direção-Geral do Território, 2011)',0,0,1294);
insert into tbl_datum_transform (epsg_nr,coord_op_code,source_crs_code, target_crs_code,coord_op_method_code,p1,p2,p3,remarks,preferred,deprecated,area_of_use_code)
values (30001,100015,4803,4326,9603,-303.861,-60.693,103.607,'Parâmetros de Transformação de Molodensky do Datum Lisboa para PT-TM06-ETRS89 (Direção-Geral do Território, 2011)',0,0,1294);
insert into tbl_datum_transform (epsg_nr,coord_op_code,source_crs_code, target_crs_code,coord_op_method_code,p1,remarks,preferred,deprecated,area_of_use_code)
values (30002,100016,4803,4258,9615,'ptLX_e89.gsb','Grelhas no formato NTv2 para a Transformação de Coordenadas do Sistema HGDLx para o Sistema PT-TM06/ETRS89 (José Alberto Gonçalves - FCUP)',1,0,1294);
insert into tbl_datum_transform (epsg_nr,coord_op_code,source_crs_code, target_crs_code,coord_op_method_code,p1,remarks,preferred,deprecated,area_of_use_code)
values (30003,100017,4803,4258,9615,'DLX_ETRS89_geo.gsb','Grelhas no formato NTv2 para a Transformação de Coordenadas do Sistema HGDLx para o Sistema PT-TM06/ETRS89 (Direção-Geral do Território)',0,0,1294);
insert into tbl_datum_transform (epsg_nr,coord_op_code,source_crs_code, target_crs_code,coord_op_method_code,p1,p2,p3,p4,p5,p6,p7,remarks,preferred,deprecated,area_of_use_code)
values (30004,100018,4274,4326,9606,-230.994,102.591,25.199,0.633,-0.239,0.900,1.950,'Parâmetros de Transformação de Bursa-Wolf do Datum 73 para PT-TM06-ETRS89 (Direção-Geral do Território, 2011)',0,0,1294);
insert into tbl_datum_transform (epsg_nr,coord_op_code,source_crs_code, target_crs_code,coord_op_method_code,p1,p2,p3,remarks,preferred,deprecated,area_of_use_code)
values (30005,100019,4274,4326,9603,-223.150,110.132,36.711,'Parâmetros de Transformação de Molodensky do Datum 73 para PT-TM06-ETRS89 (Direção-Geral do Território, 2011)',0,0,1294);
insert into tbl_datum_transform (epsg_nr,coord_op_code,source_crs_code, target_crs_code,coord_op_method_code,p1,remarks,preferred,deprecated,area_of_use_code)
values (30006,100020,4274,4258,9615,'pt73_e89.gsb','Grelhas no formato NTv2 para a Transformação de Coordenadas do Sistema HGD73 para o Sistema PT-TM06/ETRS89 (José Alberto Gonçalves - FCUP)',1,0,1294);
insert into tbl_datum_transform (epsg_nr,coord_op_code,source_crs_code, target_crs_code,coord_op_method_code,p1,remarks,preferred,deprecated,area_of_use_code)
values (30007,100021,4274,4258,9615,'D73_ETRS89_geo.gsb','Grelhas no formato NTv2 para a Transformação de Coordenadas do Sistema HGD73 para o Sistema PT-TM06/ETRS89 (Direção-Geral do Território)',0,0,1294);
Regarding the queries above, there are some codes (epsg_nr, coord_op_code) that I assigned with a sequential number, because I did not know what I should put. In coord_op_method_code, I put what seemed right to me, but please confirm.
Regarding NTv2 grids (<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://goo.gl/jDhxJB">http://goo.gl/jDhxJB</a>) I have another doubt here. On Linux, these files are placed in /usr/share/proj. On Windows, using the OSGeo4W installer, they are placed in ..\OSGeo4W64\share\proj. With QGIS standalone, they are placed at ..\Program Files\QGIS Valmiera\share\proj.
There is no possibility of copy the grid files, automatically during the installation? This will make it easier for less experienced users.
However I came across something quite odd. In the Datum Transformation window, automatically arise some strange transformations (red in the image <a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://goo.gl/iIWOuw">http://goo.gl/iIWOuw</a>). These transformations give huge errors, and I do not understand what they represent.
May it be a bug?
The transformation operation in question (epsg_nr 1571) uses as source_crs_code the 4258 (Geodetic CRS ETRS89), which is used in some target_crs_code transformations for Portugal. May it be an incorrect match between source and target codes? It is because this transformation, and these parameters, makes no sense to me.
Thank you very much!
Best regards,
Pedro</pre>
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<pre class="moz-signature" cols="72">--
Dr. Marco Hugentobler
Sourcepole - Linux & Open Source Solutions
Weberstrasse 5, CH-8004 Zürich, Switzerland
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="mailto:marco.hugentobler@sourcepole.ch">marco.hugentobler@sourcepole.ch</a> <a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://www.sourcepole.ch">http://www.sourcepole.ch</a>
Technical Advisor QGIS Project Steering Committee </pre>
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