[PROJ] Vertical CRS transformations and vertical grid shift

[Daniele Romagnoli]

Thanks! I'll check that doc.

Regards,
Daniele

On Fri, Apr 17, 2020 at 12:27 PM Even Rouault <even.rouault at spatialys.com>
wrote:

> > I'm not sure to have fully understood how the bilinear interpolation is
>
> > being used in this process.
>
>
>
> Hopefully as (loosely) described in
> http://www.epsg.org/Portals/0/373-07-2.pdf , "4.10.2 Vertical Offset by
> Interpolation of Gridded Data"
>
>
>
> Implementation starting at:
>
> https://github.com/OSGeo/PROJ/blob/master/src/grids.cpp#L3178
>
>
>
> > Could you please do an example?
>
>
>
> Left as an exercice to the reader: peek a point on a grid intersection,
> look at the value in the grid file and verify that PROJ exactly offsets
> elevation by this value. Now takes a point at the middle of 4 grid nodes,
> compute the mean, and check that PROJ applies this interpolated value.
>
>
>
> Even
>
>
>
> --
>
> Spatialys - Geospatial professional services
>
> http://www.spatialys.com
>


-- 
Regards,
Daniele Romagnoli
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