[PROJ] Preferred grid format for transformations?

[Even Rouault]

Brian,

> The National Geodetic Survey is considering changes to the grids we
> output for transformations, geoids and more and I was wondering if there
> are currently any preferred or ideal grid formats in the PROJ
> community?  I have been doing a little research as well as seen a few
> threads recently that mentioned GeoTiff, NetCDF and HDF5 but wanted to
> see if you guys had any preferences?

This is indeed a "hot" topic. I've submitted today a Request for Comments
to the PROJ (and larger) community, whose one of the main topics is a discussion about
adopting a GeoTIFF format:
https://github.com/rouault/PROJ/blob/rfc4_remote_and_geotiff_grid/docs/source/community/rfc/rfc-4.rst#grids-in-geotiff-format

> A few things that will be coming in 2022 include grids for 3D
> velocities, uncertainties for grids (geoids, transformations) and more
> so some of the things discussed like having multidimensional information
> at each node would be nice.

I assume here that by "multidimensional" you mean storing several samples per grid node,
where the grid is still 2D indexed (referenced to a geographic longitude, latitude CRS
typically) ?
The above GeoTIFF proposal should be able to allow this.

Even

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