BUG: Fix #2864 by adding the missing vrt parameters

[jmichel-otb]

• Closes Bug in WarpedVRT support of open_rasterio() #2864
• Tests added
• Fully documented, including whats-new.rst for all changes and api.rst for new API

[fmaussion]

Should I add tests for this ?

If there is a way, it would be great yes. You can build upon (or adapt) this example here:

xarray/xarray/tests/test_backends.py

Lines 3327 to 3351 in 225868d

	def test_rasterio_vrt(self):
	import rasterio
	# tmp_file default crs is UTM: CRS({'init': 'epsg:32618'}
	with create_tmp_geotiff() as (tmp_file, expected):
	with rasterio.open(tmp_file) as src:
	with rasterio.vrt.WarpedVRT(src, crs='epsg:4326') as vrt:
	expected_shape = (vrt.width, vrt.height)
	expected_crs = vrt.crs
	print(expected_crs)
	expected_res = vrt.res
	# Value of single pixel in center of image
	lon, lat = vrt.xy(vrt.width // 2, vrt.height // 2)
	expected_val = next(vrt.sample([(lon, lat)]))
	with xr.open_rasterio(vrt) as da:
	actual_shape = (da.sizes['x'], da.sizes['y'])
	actual_crs = da.crs
	print(actual_crs)
	actual_res = da.res
	actual_val = da.sel(dict(x=lon, y=lat),
	method='nearest').data
	assert actual_crs == expected_crs
	assert actual_res == expected_res
	assert actual_shape == expected_shape
	assert expected_val.all() == actual_val.all()

cc @scottyhq who wrote this code, as I don't think any of the xarray team uses this format.

Please also add a line to whats-new.rst

[pep8speaks]

Hello @jmichel-otb! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2019-04-04 09:40:50 UTC

[jmichel-otb]

@fmaussion done, let's see what CI has to say about my patches ;)

I remember reading a thread somewhere on xarray github repo discussing whether xarray should include the rasterio backend or not.

I understand that bridges between two libraries are always hard to maintain, because you need to know both products (we actually have the same kind of problem with OTB and QGis), but from a user standpoint, they need to exist somewhere. I would probably never have turned to xarray if someone with the required knowledge had not implemented the rasterio backend.

Then of course the user community should take care of maintaining those backends (this is what I am doing right now).

Bridging xarray with rasterio opens xarray to the remote sensing imagery community. And behind rasterio there is gdal, which is an awesome library with so many great capabilities (like this on-the-fly reprojection during reading I mentioned).

[fmaussion]

This looks good to me, thanks for adding a test! I'll leave it open to give some time to others if they want to have a look as well.

[scottyhq]

@jmichel-otb completely agree on your comments and think that the remote sensing community gains a lot by making these packages work well together (gdal, rasterio, xarray, dask, etc). As more people start using the rasterio backend with various use cases hopefully there will be more contributions such as this. Thanks!

[dcherian]

Thanks @jmichel-otb