[PROJ] Constant vertical offset

[Even Rouault]

Javier,

If you need a WKT2 with a coordinate operation, then you can simply wrap 
any PROJ string expressing a coordinate operation like the following:

$ projinfo "+proj=geogoffset +dh=5" -o WKT2:2019 -q

CONVERSION["PROJ-based coordinate operation",
     METHOD["PROJ-based operation method: +proj=geogoffset +dh=5"]]

Of course only interoperable in the PROJ universe.

Otherwise using Transformation::createGeographic3DOffsets() / 
createGeographic2DWithHeightOffsets() could have been an option, but if 
your source and target CRS aren't geographic, PROJ will complain when 
getting the PROJ transformation string.

Even

Le 29/11/2021 à 16:53, Javier Jimenez Shaw a écrit :
> Thanks Even
>
> Is there anything equivalent to that as Vertical CRS to use in a 
> Compound? I know it is not correct geodetically, but I want it just as 
> a WKT temporary object. I just need that PROJ is able to understand it 
> and use it in a transformation.
> That is, given a horizontal CRS, I want to create a compound (or 
> anything equivalent) with a vertical offset (as WKT2 if it makes 
> things easier)
>
> Thanks.
> .___ ._ ..._ .. . ._. .___ .. __ . _. . __..  ... .... ._ .__
> Entre dos pensamientos racionales
> hay infinitos pensamientos irracionales.
>
>
>
> On Mon, 1 Nov 2021 at 17:01, Even Rouault <even.rouault at spatialys.com 
> <mailto:even.rouault at spatialys.com>> wrote:
>
>     Javier
>
>     Le 01/11/2021 à 13:32, Javier Jimenez Shaw a écrit :
>>     Hi
>>
>>     I want to make a transformation (at the end an
>>     operation::CoordinateOperation) that replaces the geoid model
>>     with a local constant value.
>>
>>     In some cases there is public grid file for a geoid model, but I
>>     can get a (constant) undulation value (let's say 42.9m) in a
>>     (small) area of work. I would like to include this undulation
>>     value in the transformation.
>>
>>     How can I do that? is there any pipeline option for that? (I do
>>     not see a way in
>>     https://proj.org/operations/transformations/vgridshift.html
>>     <https://proj.org/operations/transformations/vgridshift.html>) Or
>>     a way to directly create the CoordinateOperation?
>
>     You can use the
>     https://proj.org/operations/transformations/geogoffset.html
>     <https://proj.org/operations/transformations/geogoffset.html> with
>     the dh parameter. This is for example used for transformation
>     EPSG:15596
>
>     Even
>
>>
>>     Thanks
>>     .___ ._ ..._ .. . ._.  .___ .. __ . _. . __..  ... .... ._ .__
>>     Entre dos pensamientos racionales
>>     hay infinitos pensamientos irracionales.
>>
>>
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>
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>
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