[PROJ] Creating a dynamic system

[Even Rouault]

for all practical purposes, it seems to be one. I don't know why it 
hasn't been formally tagged as such in EPSG. I see that back in times I 
added in CoordinateMetadata::create() an exception to check if a CRS had 
a point motion operation attached to it to allow it to be used to create 
a CoordinateMetadata object

Le 01/03/2026 à 23:46, Javier Jimenez Shaw a écrit :
> In your last PR https://github.com/OSGeo/PROJ/pull/4685/ you use 
> "NAD83(CSRS)v7" as an example, but it does not have a dynamic datum. 
> The datum is type 3, PJ_TYPE_GEODETIC_REFERENCE_FRAME.
>
> On Sun, 22 Feb 2026 at 18:32, Even Rouault 
> <even.rouault at spatialys.com> wrote:
>
>
>     Le 22/02/2026 à 15:28, Javier Jimenez Shaw via PROJ a écrit :
>     > Hi
>     >
>     > the C function proj_coordinate_metadata_create can
>     >
>     https://proj.org/en/stable/development/reference/functions.html#c.proj_coordinate_metadata_create
>     > allows to create a dynamic system with an epoch.
>     >
>     > In case the crs is not dynamic, it fails and emits an error.
>     > However I do not see how to check if a system is dynamic, to
>     call it
>     > only if really needed.
>     >
>     > Is there such a function in the C API?
>
>     checking proj_get_type() ==
>     PJ_TYPE_DYNAMIC_GEODETIC_REFERENCE_FRAME on
>     the result of proj_crs_get_datum()
>
>     -- 
>     http://www.spatialys.com
>     My software is free, but my time generally not.
>
-- 
http://www.spatialys.com
My software is free, but my time generally not.
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