Saving netcdf file as an ASC grid flips images

[chudlerk]

Using the following netcdf file for input: https://drive.google.com/file/d/1GNWuRPm1mWVXgQsqtgl1wiZFv0evTw2x/view?usp=sharing

If I read in the netcdf file an plot it, I get this image

import xarray as xr

original_file = test_nc.nc'
original_data = xr.open_dataset(original_file)['Rain Rate']
original_data = original_data.rio.set_crs('WGS84')
plt.figure()
original_data.plot()
plt.title('Original Data')
original_data.close()

If I then save the file as an ASCII grid (.asc), reopen it and plot it, the image is flipped about the y-axis. Note that the y-axis coordinates are different too. The bottom of the original image (~36.5) is the top of the ASC image below.

asc_file = 'test_asc.asc'
original_data.rio.to_raster(asc_file)
asc_data = xr.open_dataset(asc_file)['band_data']
plt.figure()
asc_data.plot()
plt.title('ASC Data')
asc_data.close()

However, if I save the image as a TIFF and reopen/plot it, the result is correct (matches the original image)

tiff_file = 'test_tiff.tiff'
original_data.rio.to_raster(tiff_file)
tiff_data = xr.open_dataset(tiff_file)['band_data']
plt.figure()
tiff_data.plot()
plt.title('TIFF Data')
tiff_data.close()

Why does saving the file as an ASCII grid flip the image?

Environment Information

(base) C:\Users\kchudler>python -c "import rioxarray; rioxarray.show_versions()"
rioxarray (0.12.2) deps:
  rasterio: 1.3.2
    xarray: 2022.9.0
      GDAL: 3.5.2
      GEOS: 3.11.0
      PROJ: 9.0.1
 PROJ DATA: C:\ProgramData\Miniconda3\Library\share\proj
 GDAL DATA: C:\ProgramData\Miniconda3\Library\share\gdal

Other python deps:
     scipy: 1.9.1
    pyproj: 3.4.0

System:
    python: 3.9.13 | packaged by conda-forge | (main, May 27 2022, 16:50:36) [MSC v.1929 64 bit (AMD64)]
executable: C:\ProgramData\Miniconda3\python.exe
   machine: Windows-10-10.0.19044-SP0

Installation method

conda install -c conda-forge rioxarray

Conda environment information (if you installed with conda):

Environment (conda list):

(base) C:\Users\kchudler>conda list | findstr "rasterio xarray gdal"
gdal                      3.5.2            py39h34c8707_1    conda-forge
libgdal                   3.5.2                hc386656_1    conda-forge
rasterio                  1.3.2            py39h223f425_0    conda-forge
rioxarray                 0.12.2             pyhd8ed1ab_0    conda-forge
xarray                    2022.9.0           pyhd8ed1ab_0    conda-forge

Details about conda and system ( conda info ):

(base) C:\Users\kchudler>conda info

     active environment : base
    active env location : C:\ProgramData\Miniconda3
            shell level : 1
       user config file : C:\Users\kchudler\.condarc
 populated config files :
          conda version : 22.9.0
    conda-build version : not installed
         python version : 3.9.13.final.0
       virtual packages : __win=0=0
                          __archspec=1=x86_64
       base environment : C:\ProgramData\Miniconda3  (writable)
      conda av data dir : C:\ProgramData\Miniconda3\etc\conda
  conda av metadata url : None
           channel URLs : https://repo.anaconda.com/pkgs/main/win-64
                          https://repo.anaconda.com/pkgs/main/noarch
                          https://repo.anaconda.com/pkgs/r/win-64
                          https://repo.anaconda.com/pkgs/r/noarch
                          https://repo.anaconda.com/pkgs/msys2/win-64
                          https://repo.anaconda.com/pkgs/msys2/noarch
          package cache : C:\ProgramData\Miniconda3\pkgs
                          C:\Users\kchudler\.conda\pkgs
                          C:\Users\kchudler\AppData\Local\conda\conda\pkgs
       envs directories : C:\ProgramData\Miniconda3\envs
                          C:\Users\kchudler\.conda\envs
                          C:\Users\kchudler\AppData\Local\conda\conda\envs
               platform : win-64
             user-agent : conda/22.9.0 requests/2.28.1 CPython/3.9.13 Windows/10 Windows/10.0.19044
          administrator : True
             netrc file : None
           offline mode : False

[snowman2]

This is indeed strange. Because it works on a GeoTiff, it makes me wonder if there is an underlying GDAL issue instead of a rioxarray issue. Probably need to find a test case using GDAL that does the same thing to verify.

[snowman2]

Same issue if I do this:

gdal_translate -of AAIGrid test_tiff.tiff test_tiff.asc

When I open the ascii data, it is flipped.

[snowman2]

Issue addressed upstream: https://github.com/OSGeo/gdal/issues/6946