[PROJ] Derived Vertical CRS

[Even Rouault]

Javier,

I've addressed this in https://github.com/OSGeo/PROJ/pull/3270.

Regarding the WKT issue, I've raised this to the OGC CRS SWG list as the 
grammar of WKT doesn't allow currently a unitless parameter, even if the 
EPSG Vertical Offset and Slope method requires it. I'd suggest using 
something like UNIT["none",1] instead of 
ANGLEUNIT["arc-second",4.8481368111E-06], until that's cleared up

Even

Le 29/07/2022 à 21:16, Javier Jimenez Shaw a écrit :
> Hi
>
> Thanks to Even's PR #3200 "Implement Vertical Offset and slope 
> transformation method", I am trying to use a Derived Vertical CRS 
> using the conversion method "Vertical Offset and Slope" (that will be 
> a perfect combination with "Affine parametric transformation" in the 
> horizontal... I hope)
>
> The WKT2 I have created is this
>
> VERTCRS["Custom Vertical",
>     BASEVERTCRS["EGM2008 height",
>         VDATUM["EGM2008 geoid"]],
>     DERIVINGCONVERSION["vertical offs. and slope",
>         METHOD["Vertical Offset and Slope",
>             ID["EPSG",1046]],
>         PARAMETER["Ordinate 1 of evaluation point",46.9166666666669,
>             ANGLEUNIT["degree",0.0174532925199433],
>             ID["EPSG",8617]],
>         PARAMETER["Ordinate 2 of evaluation point",8.18333333333361,
>             ANGLEUNIT["degree",0.0174532925199433],
>             ID["EPSG",8618]],
>         PARAMETER["Vertical Offset",-0.245,
>             LENGTHUNIT["metre",1],
>             ID["EPSG",8603]],
>         PARAMETER["Inclination in latitude",-0.21,
>             ANGLEUNIT["arc-second",4.8481368111E-06],
>             ID["EPSG",8730]],
>         PARAMETER["Inclination in longitude",-0.032,
>             ANGLEUNIT["arc-second",4.8481368111E-06],
>             ID["EPSG",8731]],
>         PARAMETER["EPSG code for Horizontal CRS",4326,
>             ANGLEUNIT["arc-second",4.8481368111E-06],
>             ID["EPSG",1037]]],
>     CS[vertical,1],
>         AXIS["gravity-related height (H)",up,
>             LENGTHUNIT["metre",1]],
>     USAGE[
>         SCOPE["unknown"],
>         AREA["World"],
>         BBOX[-90,-180,90,180]]]
>
> The first strange thing is that without the unit in the parameter 
> "EPSG code for Horizontal CRS", projinfo "$(cat derived_vertical.wkt)" 
> shows a warning:
> Warning: Parsing error : syntax error, unexpected ID. Error occurred 
> around:
>             ID["EPSG",1037]]],
>
> When I try to see how the conversion would be with the command
> projinfo -s EPSG:3855 -t "$(cat derived_vertical.wkt)"
> I get
> PROJ string:
> Error when exporting to PROJ string: Unsupported conversion method: 
> Vertical Offset and Slope
>
> Using it in a compound crs and using cs2cs does not get the proper 
> transformation neither.
>
> Am I creating the WKT2 string properly to create a derived vertical 
> crs (to be used in a compound) with that conversion method?
>
> Thanks
>
> PS. I am using master from today
> PS2. projinfo -s EPSG:5728 -t EPSG:5730 shows a coordinate operation 
> that uses "Vertical Offset and Slope", with a nice PROJ string
>
> .___ ._ ..._ .. . ._. .___ .. __ . _. . __..  ... .... ._ .__
> Entre dos pensamientos racionales
> hay infinitos pensamientos irracionales.
>
>
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