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Jun 21, 2022
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Stereographic load with scale factor #4785

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f5f0d64
Stereographic load with scale factor
Jun 8, 2022
4c37df2
Save test
Jun 21, 2022
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5 changes: 5 additions & 0 deletions lib/iris/fileformats/_nc_load_rules/helpers.py
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Original file line number Diff line number Diff line change
Expand Up @@ -417,6 +417,10 @@ def build_stereographic_coordinate_system(engine, cf_grid_var):
longitude_of_projection_origin = getattr(
cf_grid_var, CF_ATTR_GRID_LON_OF_PROJ_ORIGIN, None
)
scale_factor_at_projection_origin = getattr(
cf_grid_var, CF_ATTR_GRID_SCALE_FACTOR_AT_PROJ_ORIGIN, None
)

false_easting = getattr(cf_grid_var, CF_ATTR_GRID_FALSE_EASTING, None)
false_northing = getattr(cf_grid_var, CF_ATTR_GRID_FALSE_NORTHING, None)

Expand All @@ -426,6 +430,7 @@ def build_stereographic_coordinate_system(engine, cf_grid_var):
false_easting,
false_northing,
true_scale_lat=None,
scale_factor_at_projection_origin=scale_factor_at_projection_origin,
ellipsoid=ellipsoid,
)

Expand Down
8 changes: 4 additions & 4 deletions lib/iris/tests/results/netcdf/netcdf_stereo.cml
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Original file line number Diff line number Diff line change
Expand Up @@ -54,15 +54,15 @@
10.449, 10.5996]]" shape="(160, 256)" standard_name="longitude" units="Unit('degrees')" value_type="float32" var_name="lon"/>
</coord>
<coord datadims="[1]">
<dimCoord id="3aaada22" points="[-2.28188e+06, -2.24639e+06, -2.21091e+06, ...,
<dimCoord id="9fba0c21" points="[-2.28188e+06, -2.24639e+06, -2.21091e+06, ...,
6.69544e+06, 6.73092e+06, 6.7664e+06]" shape="(256,)" standard_name="projection_x_coordinate" units="Unit('m')" value_type="float32" var_name="x">
<stereographic central_lat="90.0" central_lon="-35.0" ellipsoid="GeogCS(6378169.0)" false_easting="0.0" false_northing="0.0" scale_factor_at_projection_origin="None" true_scale_lat="None"/>
<stereographic central_lat="90.0" central_lon="-35.0" ellipsoid="GeogCS(6378169.0)" false_easting="0.0" false_northing="0.0" scale_factor_at_projection_origin="1.0" true_scale_lat="None"/>
</dimCoord>
</coord>
<coord datadims="[0]">
<dimCoord id="27f71466" points="[-981693.0, -1.01719e+06, -1.05269e+06, ...,
<dimCoord id="f10e9ab3" points="[-981693.0, -1.01719e+06, -1.05269e+06, ...,
-6.55525e+06, -6.59075e+06, -6.62625e+06]" shape="(160,)" standard_name="projection_y_coordinate" units="Unit('m')" value_type="float32" var_name="y">
<stereographic central_lat="90.0" central_lon="-35.0" ellipsoid="GeogCS(6378169.0)" false_easting="0.0" false_northing="0.0" scale_factor_at_projection_origin="None" true_scale_lat="None"/>
<stereographic central_lat="90.0" central_lon="-35.0" ellipsoid="GeogCS(6378169.0)" false_easting="0.0" false_northing="0.0" scale_factor_at_projection_origin="1.0" true_scale_lat="None"/>
</dimCoord>
</coord>
<coord>
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23 changes: 23 additions & 0 deletions lib/iris/tests/results/unit/fileformats/netcdf/Saver/write/stereographic_scale_factor.cdl
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Original file line number Diff line number Diff line change
@@ -0,0 +1,23 @@
dimensions:
projection_x_coordinate = 4 ;
projection_y_coordinate = 3 ;
variables:
int64 air_pressure_anomaly(projection_y_coordinate, projection_x_coordinate) ;
air_pressure_anomaly:standard_name = "air_pressure_anomaly" ;
air_pressure_anomaly:grid_mapping = "stereographic" ;
int stereographic ;
stereographic:grid_mapping_name = "stereographic" ;
stereographic:longitude_of_projection_origin = 20. ;
stereographic:latitude_of_projection_origin = -10. ;
stereographic:false_easting = 500000. ;
stereographic:false_northing = -200000. ;
stereographic:scale_factor_at_projection_origin = 1.3 ;
int64 projection_y_coordinate(projection_y_coordinate) ;
projection_y_coordinate:axis = "Y" ;
projection_y_coordinate:units = "m" ;
projection_y_coordinate:standard_name = "projection_y_coordinate" ;
int64 projection_x_coordinate(projection_x_coordinate) ;
projection_x_coordinate:axis = "X" ;
projection_x_coordinate:units = "m" ;
projection_x_coordinate:standard_name = "projection_x_coordinate" ;
}
4 changes: 3 additions & 1 deletion ...ests/unit/fileformats/nc_load_rules/helpers/test_build_stereographic_coordinate_system.py
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Original file line number Diff line number Diff line change
Expand Up @@ -26,12 +26,13 @@ class TestBuildStereographicCoordinateSystem(tests.IrisTest):
def _test(self, inverse_flattening=False, no_offsets=False):
test_easting = -100
test_northing = 200
test_scale_factor = 1.2
gridvar_props = dict(
latitude_of_projection_origin=0,
longitude_of_projection_origin=0,
false_easting=test_easting,
false_northing=test_northing,
scale_factor_at_projection_origin=1,
scale_factor_at_projection_origin=test_scale_factor,
semi_major_axis=6377563.396,
)

Expand Down Expand Up @@ -61,6 +62,7 @@ def _test(self, inverse_flattening=False, no_offsets=False):
central_lon=cf_grid_var.longitude_of_projection_origin,
false_easting=test_easting,
false_northing=test_northing,
scale_factor_at_projection_origin=test_scale_factor,
ellipsoid=expected_ellipsoid,
)

Expand Down
18 changes: 16 additions & 2 deletions lib/iris/tests/unit/fileformats/netcdf/test_Saver.py
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Original file line number Diff line number Diff line change
Expand Up @@ -87,11 +87,17 @@ def _mercator_cube(self, ellipsoid=None):
cube.add_dim_coord(coord, 1)
return cube

def _stereo_cube(self, ellipsoid=None):
def _stereo_cube(self, ellipsoid=None, scale_factor=None):
data = self.array_lib.arange(12).reshape(3, 4)
cube = Cube(data, "air_pressure_anomaly")
stereo = Stereographic(
-10.0, 20.0, 500000.0, -200000.0, None, ellipsoid
-10.0,
20.0,
500000.0,
-200000.0,
None,
ellipsoid,
scale_factor_at_projection_origin=scale_factor,
)
coord = DimCoord(
np.arange(3),
Expand Down Expand Up @@ -160,6 +166,14 @@ def test_stereographic_no_ellipsoid(self):
saver.write(cube)
self.assertCDL(nc_path)

def test_stereographic_scale_factor(self):
# Create a Cube with a stereographic coordinate system.
cube = self._stereo_cube(scale_factor=1.3)
with self.temp_filename(".nc") as nc_path:
with Saver(nc_path, "NETCDF4") as saver:
saver.write(cube)
self.assertCDL(nc_path)

def _simple_cube(self, dtype):
data = self.array_lib.arange(12, dtype=dtype).reshape(3, 4)
points = np.arange(3, dtype=dtype)
Expand Down