Merge pull request OSGeo#12549 from rouault/netcdf_read_rotated_pole_without_geogcrs_def

netCDF: support reading SRS/geotransfrom from Rotated Latitude Longitude grid mapping without ellipsoid definition

Author: rouault

autotest/gdrivers/data/netcdf/rotated_pole_without_geogcrs_def.nc

@@ -6761,3 +6761,17 @@ def test_netcdf_geotransform_preserved_createcopy(tmp_path):
     dst = gdal.GetDriverByName("netCDF").CreateCopy(tmp_path / "test.nc", src)
 
     assert dst.GetGeoTransform() == src.GetGeoTransform()
+
+
+###############################################################################
+#
+
+
+@pytest.mark.require_proj(8, 2)
+def test_netcdf_read_rotated_pole_without_geogcrs_def():
+
+    ds = gdal.Open("data/netcdf/rotated_pole_without_geogcrs_def.nc")
+    assert ds.GetSpatialRef().IsDerivedGeographic()
+    assert [x for x in ds.GetGeoTransform()] == pytest.approx(
+        [144.0, 0.1, 0.0, -27.9, 0.0, -0.1]
+    )

autotest/gdrivers/netcdf.py

@@ -728,13 +728,16 @@ OGRErr OGRSpatialReference::importFromCF1(CSLConstList papszKeyValues,
         const double dfNorthPoleGridLong = FetchDoubleParam(
             papszKeyValues, CF_PP_NORTH_POLE_GRID_LONGITUDE, 0.0);
 
+        if (!bGotGeogCS)
+            SetWellKnownGeogCS("WGS84");
+
         bRotatedPole = true;
         SetDerivedGeogCRSWithPoleRotationNetCDFCFConvention(
             "Rotated_pole", dfGridNorthPoleLat, dfGridNorthPoleLong,
             dfNorthPoleGridLong);
     }
 
-    if (IsProjected())
+    if (IsProjected() && !bRotatedPole)
     {
         const char *pszProjectedCRSName =
             CSLFetchNameValue(papszKeyValues, CF_PROJECTED_CRS_NAME);
@@ -748,7 +751,7 @@ OGRErr OGRSpatialReference::importFromCF1(CSLConstList papszKeyValues,
         SetAngularUnits(SRS_UA_DEGREE, CPLAtof(SRS_UA_DEGREE_CONV));
         SetAuthority("GEOGCS|UNIT", "EPSG", 9122);
     }
-    else if (pszUnits != nullptr && !EQUAL(pszUnits, ""))
+    else if (pszUnits != nullptr && !EQUAL(pszUnits, "") && !bRotatedPole)
     {
         if (EQUAL(pszUnits, "m") || EQUAL(pszUnits, "metre") ||
             EQUAL(pszUnits, "meter"))