[PROJ] Derived Vertical CRS

[Javier Jimenez Shaw]

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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