[gdal-dev] Problem with coordinate transformation

[Laurențiu Nicola]

Hi Philippe,

The new behaviour is correct. See https://gdal.org/development/rfc/rfc73_proj6_wkt2_srsbarn.html#axis-order-issues for the axis order issue, a change made in GDAL 3.0. You can find a solution in https://github.com/OSGeo/gdal/blob/v3.5.0/MIGRATION_GUIDE.TXT#L67 (calling SetAxisMappingStrategy(OAMS_TRADITIONAL_GIS_ORDER) on every OGRSpatialReference you use.

Laurentiu

On Tue, Oct 18, 2022, at 13:43, Philippe Lelong wrote:
> Hi,
> 
> 
> 
> I have an app build against GDAL 3.4.1 and PROJ6, and the same app build against GDAL 2.1.3 and PROJ4. They are not giving the same result when using OGRCoordinateTransformation.
> 
> 
> 
> If I do
> 
> 
> 
> 
> 
>     const char *their = "GEOGCS[\"WGS 84\",DATUM[\"WGS_1984\",SPHEROID[\"WGS 84\",6378137,298.257223563,AUTHORITY[\"EPSG\",\"7030\"]],AUTHORITY[\"EPSG\",\"6326\"]],PRIMEM[\"Greenwich\",0],UNIT[\"degree\",0.0174532925199433],AUTHORITY[\"EPSG\",\"4326\"]]";
>     const char *our = "+proj=longlat +datum=WGS84 +ellps=WGS84 +no_defs +over";
>     double miX = -17.4042;
>     double miY = 35.3333;
>     OGRSpatialReference theirReference;
>     theirReference.importFromWkt((char**)&their);
>     OGRSpatialReference ourReference;
>     ourReference.importFromProj4(our);
>     OGRCoordinateTransformation *trans = OGRCreateCoordinateTransformation(&theirReference, &ourReference);
>     trans->Transform(1, &miX, &miY);
> 
> in the version build against GDAL 3.4.1/PROJ6 this code results in swapping miX and miY (i.e. miX = 35.3333 and miY = -17.4042) 
> 
> 
> The version build against GDAL 2.1.3/PROJ4 leaves miX and miY unchanged, which I believe is correct.
> 
> 
> 
> Any explanation for this behavior and which one is correct? Would I get the same result using PROJ8 ?
> 
> 
> 
> Thanks in advance
> 
> Philippe Lelong
> 
> 
> 
> 
> 
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