Xarray: Implementation of CRS storage in rasterio with PROJ.4 & WKT

[snowman2]

Continuation of the discussion from #2722 to move onto implementation details.

[snowman2]

Tag: @fmaussion @djhoese

[fmaussion]

Sorry for being late on this one. Yes, I agree that the "coordinate attribute" is worth a try.

To avoid redundancy in the name one could name the coord variable attributes simply wkt and proj4, like:

<xarray.DataArray 'crs' ()>
array(0)
Coordinates:
    crs          int64 0
Attributes:
    wkt:  PROJCS["UTM Zone 15, Northern Hemisphere",GEOGCS["WGS 84",D...
    proj4: +proj=...

[snowman2]

I definitely agree 💯 with you on avoiding redundancy. I actually had the same thought. However, part of the reason for using crs_wkt is motivated by CF 1.7 convention. I figured it was a small change that sacrifices redundancy for consistency across the community. The crs_proj4 name was just an attempt to be consistent with your original comment and the crs_wkt. But, I think renaming it to proj4 to remove redundancy is a good choice as well.

[snowman2]

@fmaussion just a ping for what are your thoughts are for next steps on this?

[snowman2]

Going to close this as it is over a year old.

For reference, WKT support is in rioxarray.
https://corteva.github.io/rioxarray/stable/examples/crs_management.html

[dcherian]

@snowman2 @djhoese It'd be nice to update our docs to link to rioxarray and other relevant packages. (e.g. here https://xarray.pydata.org/en/stable/io.html#rasterio).

Adding an example on doing these manipulations would also be very welcome.

[snowman2]

Adding an example on doing these manipulations would also be very welcome.

What types of manipulations are you thinking about? Reprojection? Export to geotiff? Clip? Reading in files?

[fmaussion]

I think we should seriously consider removing all rasterio logic in xarray and make rioxarray an optional dependency to read geotiff files with xarray.

[dcherian]

@snowman2 Any/all of those "common operations" sounds good. We don't have a single geoTIFF example: https://xarray.pydata.org/en/stable/examples.html so at this point anything would be a big improvement

I think we should seriously consider removing all rasterio logic in xarray and make rioxarray an optional dependency to read geotiff files with xarray.

:+1: Though maybe we should wait till the backends refactor is done so that things are a little more easy.

[snowman2]

@dcherian Maybe a link to these examples in that section then?
https://corteva.github.io/rioxarray/stable/examples/examples.html