Is it possible to get PROJ parameters

[djhoese]

I'm coming from using pygrib where there was a .projparams dictionary of (mostly) PROJ.4 compatible projection parameters. Does anything like this exist with cfgrib? If not, is it planned? Desired?

Xarray currently supports reading in rasterio files where it sets a "crs" attribute in the DataArray/Dataset. There has also been discussion by me and a couple others to find the best way to make a "crs" coordinate that is more useful.

For cfgrib though, I'd like to at least get access to some of the projection parameters as-is in the grib file, but initial checks by @katherinekolman with the NCEP files we want to read make it look like some are missing.

Any help is much appreciated.

[alexamici]

@djhoese sorry I didn't notice the last question of the issue. It is possible to access all keys common to all messages in a variable by adding read_keys open option, see: https://github.com/ecmwf/cfgrib#read-arbitrary-grib-keys

[vic1309]

Dear all

I am also having problems to obtain projparams using xarray. In pygrib, for instance, we can access parameters by doing
grb = grbs.select(name='10 metre U wind component')[0]
grb.projparams

Is there something similar for cfgrib? What is the read_keys for that?

Thank you in advance.

[iainrussell]

Dear @vic1309

I don't know if you're still having problems with this, but in order to select particular parameters, use filter_by_keys and to add the projection parameter, use read_keys as described on the main page: https://github.com/ecmwf/cfgrib with projString as the key to get.

Best regards,
Iain