Round data in staticmaps.nc

[hboisgon]

Kind of request

Changing existing functionality

Enhancement Description

We have the request for staticgeoms but I think it would be good practice to round all grids in staticmaps.nc.
The number of decimals does not make sense. Eg

Use case

It would produce less big file for staticmaps.nc. Not sure if it would have any impact on computation speed?

Additional Context

No response

[Huite]

Hi @hboisgon,

I saw an issue like this come up in my mentions earlier, for Wflow.jl: Deltares/Wflow.jl#314

Like I mention there: you generally don't want to round binary numbers. A float32 will always take 32 bits of memory, and a float64 will take 64 bits of memory. You might get smaller files if you turn compression on, and rounding might help a little since you are reducing the information content (so the compression algorithm will be able to find more redundancy), but you need to turn on compression in either case.

But if you're looking to reduce file sizes, I recommend investigating compression instead. NetCDF4 only supports zlib compression; e.g. Zarr uses Blosc for far more performant compression.

With regards to the physical interpretation: if you want to add that, you should probably try adding metadata instead. You could argue that a river width is never more accurate than 1 cm (for example), but doesn't generalize: e.g. if you're doing computational/numerical experiments.

And in that case you should do error propagation proper! That's stuff like this:
https://github.com/JuliaPhysics/Measurements.jl
https://pythonhosted.org/uncertainties/

And then ideally support it in an xarray package like pint does: https://xarray.dev/blog/introducing-pint-xarray