issue_comments: 409566229

Lots of good thoughts there.

I think a lot depends on who you plan on having for a user base. I like rasterio.crs.CRS, but it does require GDAL. I know GDAL is a heavy dependency (solves runtime problems and it a source of installation problems), but if your users are already using it, then it isn't too big of an ask. If not, you could look into something like pycrs. But, it looks like it hasn't been touched for a while (never a good sign). Or, there are other options, (requiring a more work & maintenance) such as re-creating the rasterio.crs.CRS object and using cython with a copy of only the spatial reference code from GDAL in the repo (might be better to create your own repo/package if you head in this direction). Or maybe someone could ask really nicely for the GDAL maintainers to consider making the spatial reference code a package on it's own (not likely, but would be really nice).

My preference to have the CRS object something created/retrieved by the accessor based on information in the file. If it is not, users will have to remove the CRS object when using to_netcdf() as the object will not be serializable and to_netcdf() will throw errors. I think allowing the user to set the CRS on the file (by adding the crs to .coords and grid_mapping to data_vars) by passing in a valid projection string (WKT, proj.4) geo.set_crs() would be a good idea. This way, when the user calls, to_netcdf() it will happily do what they want. In addition, the CRS will still be available later with the accessor when loading in with xr.open_dataset.