[gdal-dev] Zarr BLOCKSIZE in gdalmdimtranslate with variables of varying dimension

[Even Rouault]

Simon,

see the ARRAY:IF(DIM=2):BLOCKSIZE=256,256 example of 
GDALGroup::CopyFrom() mentioned at 
https://gdal.org/en/stable/doxygen/classGDALGroup.html#a28324579902842d7dbd1f93e9698b1ec

Even

Le 12/03/2025 à 09:23, Simon Lyngby Kokkendorff via gdal-dev a écrit :
> Hi list,
>
>    gdalmdimtranslate is a very handy tool e.g. to translate netCDF
> files to Zarr as it can handle huge files that xarray just chokes on.
>     I have a question regarding handling output blocksizes for the Zarr
> format for files with variables of varying dimensions though. For
> example I need to translate a netCDF file with time, z, lat, lon
> dimensions and variables which are either 4D (time, z, lat, lon), 3D
> (time, lat, lon) and 2D (lat, lon). I would like to remap chunksizes /
> blocksizes to better suit my use case. However, it seems that I can
> only specify blocksizes as e.g. -co ARRAY:BLOCKSIZE 2, 2, 128, 128 -
> which will throw an error and skip the variables that don't  have 4
> dimensions. Also, the output doesn't contain the dimension variables
> in this case. Likewise, for 4D variables if I only specify 3
> blocksizes.
>    Have tried this with gdal versions 3.8.4 and 3.4.1 with similar results.
>     So the question is if there is any way to specify blocksizes e.g.
> by dimension name? Or if the approach should rather be to just create
> 3 output Zarr folders - one for each variable dimensionality (2D, 3D
> and 4D)? I can of course manually "merge" these folders afterwards.
>
> Best regards,
> Simon
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