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I have two xarray data arrays (1. land_data, 2. climate_data) that I want to reproject and match (rio.reproject_match()):

climate_data_matched = climate_data.rio.reproject_match(land_data)
  1. Land data is a geotiff file with land_data.rio.crs = EPSG:4326. The crs attribute is accepted by rio.reproject_match().
  2. Climate data is a netcdf file with climate_data.rio.crs =

GEOGCRS["undefined",BASEGEOGCRS["undefined",DATUM["World Geodetic System 1984",ELLIPSOID["WGS 84",6378137,298.257223563,LENGTHUNIT["metre",1]],ID["EPSG",6326]],PRIMEM["Greenwich",0,ANGLEUNIT["degree",0.0174532925199433],ID["EPSG",8901]]],DERIVINGCONVERSION["Pole rotation (netCDF CF convention)",METHOD["Pole rotation (netCDF CF convention)"],PARAMETER["Grid north pole latitude (netCDF CF convention)",39.25,ANGLEUNIT["degree",0.0174532925199433,ID["EPSG",9122]]],PARAMETER["Grid north pole longitude (netCDF CF convention)",198,ANGLEUNIT["degree",0.0174532925199433,ID["EPSG",9122]]],PARAMETER["North pole grid longitude (netCDF CF convention)",0,ANGLEUNIT["degree",0.0174532925199433,ID["EPSG",9122]]]],CS[ellipsoidal,2],AXIS["longitude",east,ORDER1,ANGLEUNIT["degree",0.0174532925199433,ID["EPSG",9122]]],AXIS["latitude",north,ORDER2,ANGLEUNIT["degree",0.0174532925199433,ID["EPSG",9122]]]]

However, rio.reproject_match() does only support OGC WKT (from spatialreference.org).

PROBLEM: If I run the code as described above, the climate_data array is empty (NaN values).

My assumption is that the prefix GEOGCRS cannot be interpreted and instead I need to convert the wkt to a string starting with GEOGCS (in line with OGC WKT). How can I convert them? I converted crs = climate_data.rio.crs.to_proj4() and then wanted to use pycrs to crs = pycrs.parse.from_proj4(crs) and crs = pycrs.parse.from_ogc_wkt(crs). But I got an error parsing the proj4 string: "The specified projection name 'ob_tran' could not be found in the list of supported projections."

If I manually modify the crs of climate_data climate_data = climate_data.rio.write_crs("epsg:4326", inplace=True) and then run the code from above rio.reproject_match() works perfectly fine. But I do not know whether 'EPSG:4326' is actually to right code for the climate_data. How can I get the EPSG code from the wkt string starting with GEOGCRS?

Furthermore, I found this issue that proj4 failed in the past with GEOGCRS. And GEOGCRS is also defined in opengeospatial.org.

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  • Maybe you should update the reading program. The WKT standard says "If the WKT begins with or contains any of the following keywords, it is an older format: COMPDCS, FITTED_CS, GEOCCS, GEOGCS, LOCAL_CS, PROJCS, VERT_CS. The last characters in all these keywords are 'CS'."
    – user30184
    May 15, 2022 at 19:37
  • Can you edit your question to include the full WKT string please
    – user2856
    May 15, 2022 at 21:00
  • 1. The land data is an EPSG code and the climate data is contains the keyword GEOGCRS. so it seems that it is not an older format. 2. I added the full WKT. Maybe FYI: The climate data was a rotated grid data I changed to a regular grid. But I did not change the CRS attribute.
    – ProgMau
    May 16, 2022 at 21:13

1 Answer 1

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Looks like "Pole rotation (netCDF CF convention)" was added in PROJ 8.2:

Requires PROJ >= 8.2 to work. So, you need to have your version of pyproj/GDAL built against PROJ >= 8.2.

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