[gdal-dev] Failure with osr.CoordinateTransformationOptions()

[Even Rouault]

Le 05/03/2021 à 12:54, Stefano Iacovella a écrit :
> Hi Even,
>
> Thank you for your detailed reply.
> So if I want to use 1169 or also 1660, that is the first candidate 
> listed by
>
> projinfo -s EPSG:3003 -t EPSG:4326 --spatial-test intersects
>
> I can transform the coordinates from 3003 to 4265, that is the 
> geodetic SRS used by 3003
>
> sourceProj = osr.SpatialReference()
> sourceProj.ImportFromEPSG(3003)
>
> sourceGeo = osr.SpatialReference()
> sourceGeo.ImportFromEPSG(4265)
>
> proj2geo = osr.CoordinateTransformation(sourcePro,sourceGeo)
>
> point.Transform(proj2geo)
>
> then I can use EPSG:1169. I tried the code snippet and it seems to be 
> working properly.
> Do you think this is a correct approach?

Yes that's probably the best approach if you don't want to use PROJ 
pipelines to do it in one step.


>
> All the best
>
> Stefano
>
>
> Il giorno ven 5 mar 2021 alle ore 12:11 Even Rouault 
> <even.rouault at spatialys.com <mailto:even.rouault at spatialys.com>> ha 
> scritto:
>
>     Stefano,
>
>     urn:ogc:def:coordinateOperation:EPSG::1169 is a transformation
>     between EPSG:4265 (the geographic CRS of Monte Mario) and
>     EPSG:4326. You cannot use it directly when the source CRS is
>     EPSG:3003, which is a projected CRS based on EPSG:4265.
>
>     You could instead use
>
>     options.SetOperation("""+proj=pipeline
>       +step +inv +proj=tmerc +lat_0=0 +lon_0=9 +k=0.9996 +x_0=1500000
>     +y_0=0
>             +ellps=intl
>       +step +proj=push +v_3
>       +step +proj=cart +ellps=intl
>       +step +proj=helmert +x=-225 +y=-65 +z=9
>       +step +inv +proj=cart +ellps=WGS84
>       +step +proj=pop +v_3
>       +step +proj=unitconvert +xy_in=rad +xy_out=deg
>       +step +proj=axisswap +order=2,1""")
>
>     as suggested by the output of projinfo -s EPSG:3003 -t EPSG:4326
>     --spatial-test intersects
>
>     Even
>
>     Le 05/03/2021 à 09:42, Stefano Iacovella a écrit :
>>     Hi all,
>>
>>     I am trying to use GDAL, via Python bindings, to convert coordinates.
>>     I would like to select a specific transformation when converting
>>     among CRS with different Datums. Reading the documentation my
>>     understanding is that I need to create a
>>     osr.CoordinateTransformation with options parameter valorized
>>     properly.
>>     I am using binaries from OSGEO4WIN, the release are 3.1.4 for
>>     GDAL and 6.3.2 for PROJ
>>     This is a code snippet I am using to debug:
>>
>>     from osgeo import ogr
>>     from osgeo import osr
>>
>>     source = osr.SpatialReference()
>>     source.ImportFromEPSG(3003)
>>
>>     target = osr.SpatialReference()
>>     target.ImportFromEPSG(4326)
>>
>>     options = osr.CoordinateTransformationOptions()
>>     options.SetOperation("urn:ogc:def:coordinateOperation:EPSG::1169")
>>     transform = osr.CoordinateTransformation(source, target, options)
>>
>>     point = ogr.CreateGeometryFromWkt("POINT (1622987 4756952)")
>>     point.Transform(transform)
>>
>>     print point.ExportToWkt()
>>
>>     I have no errors running it but the coordinates of the point,
>>     after the transformation, are infinite. If I create the
>>     CoordinateTransformation without options like this:
>>
>>     transform = osr.CoordinateTransformation(source, target)
>>
>>     The point coordinates after transformation are ok but of course
>>     the conversion is performed using the Coordinate Operation
>>     automatically selected by the system.
>>     Am I doing something wrong?
>>
>>     Thank you in advance for your help.
>>
>>     All the best,
>>
>>     Stefano
>>
>>
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>
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>
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