[PROJ] [gdal-dev] OGRCreateCoordinateTransformation()

[Even Rouault]

Actually my below statement is not completely true
>
> And the ABRIDGEDTRANSFORMATION[]  syntax cannot be used for vertical 
> transformations where the geographic CRS would not be the 
> interpolation CRS.
>
https://github.com/OSGeo/PROJ/pull/3134 should improve this, by using 
the approach used in the EPSG database using a PARAMETER["EPSG code for 
Interpolation CRS",7886]

So something like below could be used to convey the interpolation CRS

BOUNDCRS[
     SOURCECRS[
         VERTCRS["unknown",
             VDATUM["unknown using geoidgrids=@foo.gtx"],
             CS[vertical,1],
                 AXIS["gravity-related height (H)",up,
                     LENGTHUNIT["metre",1,
                         ID["EPSG",9001]]]]],
     TARGETCRS[
         GEOGCRS["WGS 84",
             DATUM["World Geodetic System 1984",
                 ELLIPSOID["WGS 84",6378137,298.257223563,
                     LENGTHUNIT["metre",1]]],
             PRIMEM["Greenwich",0,
                 ANGLEUNIT["degree",0.0174532925199433]],
             CS[ellipsoidal,3],
                 AXIS["latitude",north,
                     ORDER[1],
                     ANGLEUNIT["degree",0.0174532925199433]],
                 AXIS["longitude",east,
                     ORDER[2],
                     ANGLEUNIT["degree",0.0174532925199433]],
                 AXIS["ellipsoidal height",up,
                     ORDER[3],
                     LENGTHUNIT["metre",1]],
             ID["EPSG",4979]]],
     ABRIDGEDTRANSFORMATION["unknown to WGS84 ellipsoidal height",
         METHOD["GravityRelatedHeight to Geographic3D"],
         PARAMETERFILE["Geoid (height correction) model file","@foo.gtx",
             ID["EPSG",8666]],
         PARAMETER["EPSG code for Interpolation CRS",7886]]]

Even

>
> -- 
> http://www.spatialys.com
> My software is free, but my time generally not.
>
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-- 
http://www.spatialys.com
My software is free, but my time generally not.