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 (http://goo.gl/jDhxJB) 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
imagehttp://goo.gl/iIWOuw). 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
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