<div dir="ltr"><div>Hi all,</div><div><br></div><div>I'm trying to understand what is the transformation used by default by GDAL/OGR.</div><div><br></div><div>For instance, the transformation from EPSG:20790 to EPSG:3763 has two candidates on PROJ:</div><div><br></div><div>C:\OSGeo4W>projinfo -s EPSG:20790 -t EPSG:3763<br>Candidate operations found: 2<br>-------------------------------------<br>Operation No. 1:<br><br>unknown id, Inverse of Portuguese National Grid + Lisbon (Lisbon) to Lisbon (1) + Lisbon to ETRS89 (4) + Portugual TM06, 0.1 m, Portugal - mainland - onshore.<br><br>PROJ string:<br>+proj=pipeline<br> +step +inv +proj=tmerc +lat_0=39.6666666666667 +lon_0=1 +k=1 +x_0=200000<br> +y_0=300000 +ellps=intl +pm=lisbon<br> +step +proj=hgridshift +grids=pt_dgt_DLx_ETRS89_geo.tif<br> +step +proj=tmerc +lat_0=39.6682583333333 +lon_0=-8.13310833333333 +k=1 +x_0=0<br> +y_0=0 +ellps=GRS80<br><br>WKT2:2019 string:<br>CONCATENATEDOPERATION["Inverse of Portuguese National Grid + Lisbon (Lisbon) to Lisbon (1) + Lisbon to ETRS89 (4) + Portugual TM06",<br> SOURCECRS[<br> PROJCRS["Lisbon (Lisbon) / Portuguese National Grid",<br> BASEGEOGCRS["Lisbon (Lisbon)",<br> DATUM["Lisbon 1937 (Lisbon)",<br> ELLIPSOID["International 1924",6378388,297,<br> LENGTHUNIT["metre",1]]],<br> PRIMEM["Lisbon",-9.13190611111111,<br> ANGLEUNIT["degree",0.0174532925199433]],<br> ID["EPSG",4803]],<br> CONVERSION["Portuguese National Grid",<br> METHOD["Transverse Mercator",<br> ID["EPSG",9807]],<br> PARAMETER["Latitude of natural origin",39.6666666666667,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8801]],<br> PARAMETER["Longitude of natural origin",1,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8802]],<br> PARAMETER["Scale factor at natural origin",1,<br> SCALEUNIT["unity",1],<br> ID["EPSG",8805]],<br> PARAMETER["False easting",200000,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8806]],<br> PARAMETER["False northing",300000,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8807]]],<br> CS[Cartesian,2],<br> AXIS["easting (X)",east,<br> ORDER[1],<br> LENGTHUNIT["metre",1]],<br> AXIS["northing (Y)",north,<br> ORDER[2],<br> LENGTHUNIT["metre",1]],<br> ID["EPSG",20790]]],<br> TARGETCRS[<br> PROJCRS["ETRS89 / Portugal TM06",<br> BASEGEOGCRS["ETRS89",<br> ENSEMBLE["European Terrestrial Reference System 1989 ensemble",<br> MEMBER["European Terrestrial Reference Frame 1989"],<br> MEMBER["European Terrestrial Reference Frame 1990"],<br> MEMBER["European Terrestrial Reference Frame 1991"],<br> MEMBER["European Terrestrial Reference Frame 1992"],<br> MEMBER["European Terrestrial Reference Frame 1993"],<br> MEMBER["European Terrestrial Reference Frame 1994"],<br> MEMBER["European Terrestrial Reference Frame 1996"],<br> MEMBER["European Terrestrial Reference Frame 1997"],<br> MEMBER["European Terrestrial Reference Frame 2000"],<br> MEMBER["European Terrestrial Reference Frame 2005"],<br> MEMBER["European Terrestrial Reference Frame 2014"],<br> ELLIPSOID["GRS 1980",6378137,298.257222101,<br> LENGTHUNIT["metre",1]],<br> ENSEMBLEACCURACY[0.1]],<br> PRIMEM["Greenwich",0,<br> ANGLEUNIT["degree",0.0174532925199433]],<br> ID["EPSG",4258]],<br> CONVERSION["Portugual TM06",<br> METHOD["Transverse Mercator",<br> ID["EPSG",9807]],<br> PARAMETER["Latitude of natural origin",39.6682583333333,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8801]],<br> PARAMETER["Longitude of natural origin",-8.13310833333333,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8802]],<br> PARAMETER["Scale factor at natural origin",1,<br> SCALEUNIT["unity",1],<br> ID["EPSG",8805]],<br> PARAMETER["False easting",0,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8806]],<br> PARAMETER["False northing",0,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8807]]],<br> CS[Cartesian,2],<br> AXIS["easting (X)",east,<br> ORDER[1],<br> LENGTHUNIT["metre",1]],<br> AXIS["northing (Y)",north,<br> ORDER[2],<br> LENGTHUNIT["metre",1]],<br> ID["EPSG",3763]]],<br> STEP[<br> CONVERSION["Inverse of Portuguese National Grid",<br> METHOD["Inverse of Transverse Mercator",<br> ID["INVERSE(EPSG)",9807]],<br> PARAMETER["Latitude of natural origin",39.6666666666667,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8801]],<br> PARAMETER["Longitude of natural origin",1,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8802]],<br> PARAMETER["Scale factor at natural origin",1,<br> SCALEUNIT["unity",1],<br> ID["EPSG",8805]],<br> PARAMETER["False easting",200000,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8806]],<br> PARAMETER["False northing",300000,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8807]],<br> ID["INVERSE(EPSG)",19936]]],<br> STEP[<br> COORDINATEOPERATION["Lisbon (Lisbon) to Lisbon (1)",<br> VERSION["IGC-Prt"],<br> SOURCECRS[<br> GEOGCRS["Lisbon (Lisbon)",<br> DATUM["Lisbon 1937 (Lisbon)",<br> ELLIPSOID["International 1924",6378388,297,<br> LENGTHUNIT["metre",1]]],<br> PRIMEM["Lisbon",-9.13190611111111,<br> ANGLEUNIT["degree",0.0174532925199433]],<br> CS[ellipsoidal,2],<br> AXIS["geodetic latitude (Lat)",north,<br> ORDER[1],<br> ANGLEUNIT["degree",0.0174532925199433]],<br> AXIS["geodetic longitude (Lon)",east,<br> ORDER[2],<br> ANGLEUNIT["degree",0.0174532925199433]],<br> ID["EPSG",4803]]],<br> TARGETCRS[<br> GEOGCRS["Lisbon",<br> DATUM["Lisbon 1937",<br> ELLIPSOID["International 1924",6378388,297,<br> LENGTHUNIT["metre",1]]],<br> PRIMEM["Greenwich",0,<br> ANGLEUNIT["degree",0.0174532925199433]],<br> CS[ellipsoidal,2],<br> AXIS["geodetic latitude (Lat)",north,<br> ORDER[1],<br> ANGLEUNIT["degree",0.0174532925199433]],<br> AXIS["geodetic longitude (Lon)",east,<br> ORDER[2],<br> ANGLEUNIT["degree",0.0174532925199433]],<br> ID["EPSG",4207]]],<br> METHOD["Longitude rotation",<br> ID["EPSG",9601]],<br> PARAMETER["Longitude offset",-9.13190611111111,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8602]],<br> OPERATIONACCURACY[0.0],<br> ID["EPSG",1756]]],<br> STEP[<br> COORDINATEOPERATION["Lisbon to ETRS89 (4)",<br> SOURCECRS[<br> GEOGCRS["Lisbon",<br> DATUM["Lisbon 1937",<br> ELLIPSOID["International 1924",6378388,297,<br> LENGTHUNIT["metre",1]]],<br> PRIMEM["Greenwich",0,<br> ANGLEUNIT["degree",0.0174532925199433]],<br> CS[ellipsoidal,2],<br> AXIS["geodetic latitude (Lat)",north,<br> ORDER[1],<br> ANGLEUNIT["degree",0.0174532925199433]],<br> AXIS["geodetic longitude (Lon)",east,<br> ORDER[2],<br> ANGLEUNIT["degree",0.0174532925199433]],<br> ID["EPSG",4207]]],<br> TARGETCRS[<br> GEOGCRS["ETRS89",<br> ENSEMBLE["European Terrestrial Reference System 1989 ensemble",<br> MEMBER["European Terrestrial Reference Frame 1989"],<br> MEMBER["European Terrestrial Reference Frame 1990"],<br> MEMBER["European Terrestrial Reference Frame 1991"],<br> MEMBER["European Terrestrial Reference Frame 1992"],<br> MEMBER["European Terrestrial Reference Frame 1993"],<br> MEMBER["European Terrestrial Reference Frame 1994"],<br> MEMBER["European Terrestrial Reference Frame 1996"],<br> MEMBER["European Terrestrial Reference Frame 1997"],<br> MEMBER["European Terrestrial Reference Frame 2000"],<br> MEMBER["European Terrestrial Reference Frame 2005"],<br> MEMBER["European Terrestrial Reference Frame 2014"],<br> ELLIPSOID["GRS 1980",6378137,298.257222101,<br> LENGTHUNIT["metre",1]],<br> ENSEMBLEACCURACY[0.1]],<br> PRIMEM["Greenwich",0,<br> ANGLEUNIT["degree",0.0174532925199433]],<br> CS[ellipsoidal,2],<br> AXIS["geodetic latitude (Lat)",north,<br> ORDER[1],<br> ANGLEUNIT["degree",0.0174532925199433]],<br> AXIS["geodetic longitude (Lon)",east,<br> ORDER[2],<br> ANGLEUNIT["degree",0.0174532925199433]],<br> ID["EPSG",4258]]],<br> METHOD["HORIZONTAL_SHIFT_GTIFF"],<br> PARAMETERFILE["Latitude and longitude difference file","pt_dgt_DLx_ETRS89_geo.tif"],<br> OPERATIONACCURACY[0.1],<br> ID["DERIVED_FROM(EPSG)",6188],<br> REMARK["Derived from 1129 common stations in the national geodetic network. Residuals at 130 further test points average 0.09m, maximum 0.30m."]]],<br> STEP[<br> CONVERSION["Portugual TM06",<br> METHOD["Transverse Mercator",<br> ID["EPSG",9807]],<br> PARAMETER["Latitude of natural origin",39.6682583333333,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8801]],<br> PARAMETER["Longitude of natural origin",-8.13310833333333,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8802]],<br> PARAMETER["Scale factor at natural origin",1,<br> SCALEUNIT["unity",1],<br> ID["EPSG",8805]],<br> PARAMETER["False easting",0,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8806]],<br> PARAMETER["False northing",0,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8807]],<br> ID["EPSG",19853]]],<br> USAGE[<br> SCOPE["unknown"],<br> AREA["Portugal - mainland - onshore."],<br> BBOX[36.95,-9.56,42.16,-6.19]]]<br><br>-------------------------------------<br>Operation No. 2:<br><br>unknown id, Inverse of Portuguese National Grid + Lisbon (Lisbon) to Lisbon (1) + Lisbon to ETRS89 (3) + Portugual TM06, 2.5 m, Portugal - mainland - onshore.<br><br>PROJ string:<br>+proj=pipeline<br> +step +inv +proj=tmerc +lat_0=39.6666666666667 +lon_0=1 +k=1 +x_0=200000<br> +y_0=300000 +ellps=intl +pm=lisbon<br> +step +proj=push +v_3<br> +step +proj=cart +ellps=intl<br> +step +proj=helmert +x=-303.861 +y=-60.693 +z=103.607<br> +step +inv +proj=cart +ellps=GRS80<br> +step +proj=pop +v_3<br> +step +proj=tmerc +lat_0=39.6682583333333 +lon_0=-8.13310833333333 +k=1 +x_0=0<br> +y_0=0 +ellps=GRS80<br><br>WKT2:2019 string:<br>CONCATENATEDOPERATION["Inverse of Portuguese National Grid + Lisbon (Lisbon) to Lisbon (1) + Lisbon to ETRS89 (3) + Portugual TM06",<br> SOURCECRS[<br> PROJCRS["Lisbon (Lisbon) / Portuguese National Grid",<br> BASEGEOGCRS["Lisbon (Lisbon)",<br> DATUM["Lisbon 1937 (Lisbon)",<br> ELLIPSOID["International 1924",6378388,297,<br> LENGTHUNIT["metre",1]]],<br> PRIMEM["Lisbon",-9.13190611111111,<br> ANGLEUNIT["degree",0.0174532925199433]],<br> ID["EPSG",4803]],<br> CONVERSION["Portuguese National Grid",<br> METHOD["Transverse Mercator",<br> ID["EPSG",9807]],<br> PARAMETER["Latitude of natural origin",39.6666666666667,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8801]],<br> PARAMETER["Longitude of natural origin",1,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8802]],<br> PARAMETER["Scale factor at natural origin",1,<br> SCALEUNIT["unity",1],<br> ID["EPSG",8805]],<br> PARAMETER["False easting",200000,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8806]],<br> PARAMETER["False northing",300000,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8807]]],<br> CS[Cartesian,2],<br> AXIS["easting (X)",east,<br> ORDER[1],<br> LENGTHUNIT["metre",1]],<br> AXIS["northing (Y)",north,<br> ORDER[2],<br> LENGTHUNIT["metre",1]],<br> ID["EPSG",20790]]],<br> TARGETCRS[<br> PROJCRS["ETRS89 / Portugal TM06",<br> BASEGEOGCRS["ETRS89",<br> ENSEMBLE["European Terrestrial Reference System 1989 ensemble",<br> MEMBER["European Terrestrial Reference Frame 1989"],<br> MEMBER["European Terrestrial Reference Frame 1990"],<br> MEMBER["European Terrestrial Reference Frame 1991"],<br> MEMBER["European Terrestrial Reference Frame 1992"],<br> MEMBER["European Terrestrial Reference Frame 1993"],<br> MEMBER["European Terrestrial Reference Frame 1994"],<br> MEMBER["European Terrestrial Reference Frame 1996"],<br> MEMBER["European Terrestrial Reference Frame 1997"],<br> MEMBER["European Terrestrial Reference Frame 2000"],<br> MEMBER["European Terrestrial Reference Frame 2005"],<br> MEMBER["European Terrestrial Reference Frame 2014"],<br> ELLIPSOID["GRS 1980",6378137,298.257222101,<br> LENGTHUNIT["metre",1]],<br> ENSEMBLEACCURACY[0.1]],<br> PRIMEM["Greenwich",0,<br> ANGLEUNIT["degree",0.0174532925199433]],<br> ID["EPSG",4258]],<br> CONVERSION["Portugual TM06",<br> METHOD["Transverse Mercator",<br> ID["EPSG",9807]],<br> PARAMETER["Latitude of natural origin",39.6682583333333,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8801]],<br> PARAMETER["Longitude of natural origin",-8.13310833333333,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8802]],<br> PARAMETER["Scale factor at natural origin",1,<br> SCALEUNIT["unity",1],<br> ID["EPSG",8805]],<br> PARAMETER["False easting",0,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8806]],<br> PARAMETER["False northing",0,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8807]]],<br> CS[Cartesian,2],<br> AXIS["easting (X)",east,<br> ORDER[1],<br> LENGTHUNIT["metre",1]],<br> AXIS["northing (Y)",north,<br> ORDER[2],<br> LENGTHUNIT["metre",1]],<br> ID["EPSG",3763]]],<br> STEP[<br> CONVERSION["Inverse of Portuguese National Grid",<br> METHOD["Inverse of Transverse Mercator",<br> ID["INVERSE(EPSG)",9807]],<br> PARAMETER["Latitude of natural origin",39.6666666666667,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8801]],<br> PARAMETER["Longitude of natural origin",1,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8802]],<br> PARAMETER["Scale factor at natural origin",1,<br> SCALEUNIT["unity",1],<br> ID["EPSG",8805]],<br> PARAMETER["False easting",200000,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8806]],<br> PARAMETER["False northing",300000,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8807]],<br> ID["INVERSE(EPSG)",19936]]],<br> STEP[<br> COORDINATEOPERATION["Lisbon (Lisbon) to Lisbon (1)",<br> VERSION["IGC-Prt"],<br> SOURCECRS[<br> GEOGCRS["Lisbon (Lisbon)",<br> DATUM["Lisbon 1937 (Lisbon)",<br> ELLIPSOID["International 1924",6378388,297,<br> LENGTHUNIT["metre",1]]],<br> PRIMEM["Lisbon",-9.13190611111111,<br> ANGLEUNIT["degree",0.0174532925199433]],<br> CS[ellipsoidal,2],<br> AXIS["geodetic latitude (Lat)",north,<br> ORDER[1],<br> ANGLEUNIT["degree",0.0174532925199433]],<br> AXIS["geodetic longitude (Lon)",east,<br> ORDER[2],<br> ANGLEUNIT["degree",0.0174532925199433]],<br> ID["EPSG",4803]]],<br> TARGETCRS[<br> GEOGCRS["Lisbon",<br> DATUM["Lisbon 1937",<br> ELLIPSOID["International 1924",6378388,297,<br> LENGTHUNIT["metre",1]]],<br> PRIMEM["Greenwich",0,<br> ANGLEUNIT["degree",0.0174532925199433]],<br> CS[ellipsoidal,2],<br> AXIS["geodetic latitude (Lat)",north,<br> ORDER[1],<br> ANGLEUNIT["degree",0.0174532925199433]],<br> AXIS["geodetic longitude (Lon)",east,<br> ORDER[2],<br> ANGLEUNIT["degree",0.0174532925199433]],<br> ID["EPSG",4207]]],<br> METHOD["Longitude rotation",<br> ID["EPSG",9601]],<br> PARAMETER["Longitude offset",-9.13190611111111,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8602]],<br> OPERATIONACCURACY[0.0],<br> ID["EPSG",1756]]],<br> STEP[<br> COORDINATEOPERATION["Lisbon to ETRS89 (3)",<br> VERSION["CGC-Prt 2009 7m"],<br> SOURCECRS[<br> GEOGCRS["Lisbon",<br> DATUM["Lisbon 1937",<br> ELLIPSOID["International 1924",6378388,297,<br> LENGTHUNIT["metre",1]]],<br> PRIMEM["Greenwich",0,<br> ANGLEUNIT["degree",0.0174532925199433]],<br> CS[ellipsoidal,2],<br> AXIS["geodetic latitude (Lat)",north,<br> ORDER[1],<br> ANGLEUNIT["degree",0.0174532925199433]],<br> AXIS["geodetic longitude (Lon)",east,<br> ORDER[2],<br> ANGLEUNIT["degree",0.0174532925199433]],<br> ID["EPSG",4207]]],<br> TARGETCRS[<br> GEOGCRS["ETRS89",<br> ENSEMBLE["European Terrestrial Reference System 1989 ensemble",<br> MEMBER["European Terrestrial Reference Frame 1989"],<br> MEMBER["European Terrestrial Reference Frame 1990"],<br> MEMBER["European Terrestrial Reference Frame 1991"],<br> MEMBER["European Terrestrial Reference Frame 1992"],<br> MEMBER["European Terrestrial Reference Frame 1993"],<br> MEMBER["European Terrestrial Reference Frame 1994"],<br> MEMBER["European Terrestrial Reference Frame 1996"],<br> MEMBER["European Terrestrial Reference Frame 1997"],<br> MEMBER["European Terrestrial Reference Frame 2000"],<br> MEMBER["European Terrestrial Reference Frame 2005"],<br> MEMBER["European Terrestrial Reference Frame 2014"],<br> ELLIPSOID["GRS 1980",6378137,298.257222101,<br> LENGTHUNIT["metre",1]],<br> ENSEMBLEACCURACY[0.1]],<br> PRIMEM["Greenwich",0,<br> ANGLEUNIT["degree",0.0174532925199433]],<br> CS[ellipsoidal,2],<br> AXIS["geodetic latitude (Lat)",north,<br> ORDER[1],<br> ANGLEUNIT["degree",0.0174532925199433]],<br> AXIS["geodetic longitude (Lon)",east,<br> ORDER[2],<br> ANGLEUNIT["degree",0.0174532925199433]],<br> ID["EPSG",4258]]],<br> METHOD["Geocentric translations (geog2D domain)",<br> ID["EPSG",9603]],<br> PARAMETER["X-axis translation",-303.861,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8605]],<br> PARAMETER["Y-axis translation",-60.693,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8606]],<br> PARAMETER["Z-axis translation",103.607,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8607]],<br> OPERATIONACCURACY[2.5],<br> ID["EPSG",5038],<br> REMARK["Derived in July 2009 from 119 common stations. Average residual at 833 test points 2.5m, maximum 7m. Info source also gives a Position Vector tfm which is of similar accuracy. Replaces Lisbon to ETRS89 (2) (tfm code 1997)."]]],<br> STEP[<br> CONVERSION["Portugual TM06",<br> METHOD["Transverse Mercator",<br> ID["EPSG",9807]],<br> PARAMETER["Latitude of natural origin",39.6682583333333,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8801]],<br> PARAMETER["Longitude of natural origin",-8.13310833333333,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8802]],<br> PARAMETER["Scale factor at natural origin",1,<br> SCALEUNIT["unity",1],<br> ID["EPSG",8805]],<br> PARAMETER["False easting",0,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8806]],<br> PARAMETER["False northing",0,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8807]],<br> ID["EPSG",19853]]],<br> USAGE[<br> SCOPE["unknown"],<br> AREA["Portugal - mainland - onshore."],<br> BBOX[36.95,-9.56,42.16,-6.19]]]</div><div><br></div><div>Operation no. 1 uses grids and has
an accuracy of about 0.1 meters, compared to operation no. 2 that uses a
Molodensky
transformation and has an accuracy of
2.5 m. <br></div><div><br></div><div>So, in theory, operation
no. 1 should be used by default.</div><div><br></div><div>However, testing with gdaltransform:</div><div><br></div><div>C:\OSGeo4W>gdaltransform -s_srs EPSG:20790 -t_srs EPSG:3763<br>Enter X Y [Z [T]] values separated by space, and press Return.<br>286415 431434<br><b>86412.5265012686 131433.856093867 0</b></div><div><br></div><div>Using the grids on QGIS and on a web application of the institution that has produced the NTv2 grids used on PROJ, the transformation output is</div><div><b>86412.426 131434.171</b></div><div><br></div><div>The difference is not huge, but this makes me believe that operations like gdalwarp or ogr2ogr do not use the
operation
no. 1 by default. Am I right? Could this be a bug? Or is there a way to force the operation used? How is the decision managed by GDAL/OGR?</div><div><br></div><div>Thank you very much!</div><div><br></div><div>Best regards,</div><div>Pedro Venâncio<br></div></div>