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Fix geostationary axis handling in CF writer #1040

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merged 4 commits into from
Jan 10, 2020
Merged

Fix geostationary axis handling in CF writer #1040

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d332f39
Fix geostationary axis handling in CF writer
djhoese Jan 9, 2020
bc16a99
Add omerc test to CF writer
Jan 9, 2020
37b126e
Force appveyor to libtiff build 2
djhoese Jan 9, 2020
9ba406e
Force appveyor to numpy 1.16
djhoese Jan 9, 2020
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2 changes: 1 addition & 1 deletion appveyor.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@ environment:
- PYTHON: "C:\\Python37_64"
PYTHON_VERSION: "3.7"
PYTHON_ARCH: "64"
NUMPY_VERSION: "stable"
NUMPY_VERSION: "1.16"

install:
- "git clone --depth 1 git://github.com/astropy/ci-helpers.git"
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95 changes: 78 additions & 17 deletions satpy/tests/writer_tests/test_cf.py
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Original file line number Diff line number Diff line change
Expand Up @@ -743,6 +743,15 @@ def test_area2gridmapping(self):
import pyresample.geometry
from satpy.writers.cf_writer import area2gridmapping

def _gm_matches(gmapping, expected):
"""Assert that all keys in ``expected`` match the values in ``gmapping``."""
for attr_key, attr_val in expected.attrs.items():
test_val = gmapping.attrs[attr_key]
if attr_val is None or isinstance(attr_val, str):
self.assertEqual(test_val, attr_val)
else:
np.testing.assert_almost_equal(test_val, attr_val, decimal=3)

ds_base = xr.DataArray(data=[[1, 2], [3, 4]], dims=('y', 'x'), coords={'y': [1, 2], 'x': [3, 4]},
attrs={'name': 'var1'})

Expand All @@ -759,8 +768,8 @@ def test_area2gridmapping(self):
area_extent=[-1, -1, 1, 1])
geos_expected = xr.DataArray(data=0,
attrs={'perspective_point_height': h,
'latitude_of_projection_origin': None,
'longitude_of_projection_origin': None,
'latitude_of_projection_origin': 0,
'longitude_of_projection_origin': 0,
'grid_mapping_name': 'geostationary',
'semi_major_axis': a,
'semi_minor_axis': b,
Expand All @@ -772,7 +781,7 @@ def test_area2gridmapping(self):
res, grid_mapping = area2gridmapping(ds)

self.assertEqual(res.attrs['grid_mapping'], 'geos')
self.assertEqual(grid_mapping, geos_expected)
_gm_matches(grid_mapping, geos_expected)

# b) Projection does not have a corresponding CF representation (COSMO)
cosmo7 = pyresample.geometry.AreaDefinition(
Expand All @@ -784,8 +793,6 @@ def test_area2gridmapping(self):
width=597, height=510,
area_extent=[-1812933, -1003565, 814056, 1243448]
)
proj_str = '+proj=ob_tran +ellps=WGS84 +lat_0=46.0 +lon_0=4.535 +o_proj=stere +o_lat_p=90.0 +o_lon_p=-5.465'
cosmo_expected = xr.DataArray(data=0, attrs={'name': 'proj4', 'proj4': proj_str})

ds = ds_base.copy()
ds.attrs['area'] = cosmo7
Expand All @@ -801,31 +808,25 @@ def test_area2gridmapping(self):
self.assertEqual(proj_dict['proj'], 'ob_tran')
self.assertEqual(proj_dict['o_proj'], 'stere')
self.assertEqual(proj_dict['ellps'], 'WGS84')
self.assertEqual(grid_mapping, cosmo_expected)
self.assertEqual(grid_mapping.attrs['name'], 'proj4')

# c) Projection Transverse Mercator
lat_0 = 36.5
lon_0 = 15.0
lat_ts = 36.5

tmerc = pyresample.geometry.AreaDefinition(
area_id='tmerc',
description='tmerc',
proj_id='tmerc',
projection={'proj': 'tmerc', 'ellps': 'WGS84', 'lat_0': 36.5, 'lon_0': 15.0, 'lat_ts': 36.5},
projection={'proj': 'tmerc', 'ellps': 'WGS84', 'lat_0': 36.5, 'lon_0': 15.0},
width=2, height=2,
area_extent=[-1, -1, 1, 1])

tmerc_expected = xr.DataArray(data=0,
attrs={'azimuth_of_central_line': 'alpha',
'latitude_of_projection_origin': lat_0,
'longitude_of_projection_origin': lon_0,
'latitude_of_meridian_ts': lat_ts,
attrs={'latitude_of_projection_origin': lat_0,
'longitude_of_central_meridian': lon_0,
'grid_mapping_name': 'transverse_mercator',
'reference_ellipsoid_name': ('ellps', 'WGS84'),
'prime_meridian_name': ('pm', 'Greenwich'),
'horizontal_datum_name': ('datum', 'unknown'),
'geographic_crs_name': 'unknown',
'reference_ellipsoid_name': 'WGS84',
'false_easting': 0.,
'false_northing': 0.,
'name': 'tmerc'})
Expand All @@ -834,7 +835,67 @@ def test_area2gridmapping(self):
ds.attrs['area'] = tmerc
res, grid_mapping = area2gridmapping(ds)
self.assertEqual(res.attrs['grid_mapping'], 'tmerc')
self.assertEqual(grid_mapping, tmerc_expected)
_gm_matches(grid_mapping, tmerc_expected)

# d) Projection that has a representation but no explicit a/b
h = 35785831.
geos = pyresample.geometry.AreaDefinition(
area_id='geos',
description='geos',
proj_id='geos',
projection={'proj': 'geos', 'h': h, 'datum': 'WGS84', 'ellps': 'GRS80'},
width=2, height=2,
area_extent=[-1, -1, 1, 1])
geos_expected = xr.DataArray(data=0,
attrs={'perspective_point_height': h,
'latitude_of_projection_origin': 0,
'longitude_of_projection_origin': 0,
'grid_mapping_name': 'geostationary',
'semi_major_axis': 6378137.0,
'semi_minor_axis': 6356752.314,
'sweep_axis': None,
'name': 'geos'})

ds = ds_base.copy()
ds.attrs['area'] = geos
res, grid_mapping = area2gridmapping(ds)

self.assertEqual(res.attrs['grid_mapping'], 'geos')
_gm_matches(grid_mapping, geos_expected)

# e) oblique Mercator
area = pyresample.geometry.AreaDefinition(
area_id='omerc_otf',
description='On-the-fly omerc area',
proj_id='omerc',
projection={'alpha': '9.02638777018478', 'ellps': 'WGS84', 'gamma': '0', 'k': '1',
'lat_0': '-0.256794486098476', 'lonc': '13.7888658224205',
'proj': 'omerc', 'units': 'm'},
width=2837,
height=5940,
area_extent=[-1460463.0893, 3455291.3877, 1538407.1158, 9615788.8787]
)

omerc_dict = {'name': 'omerc',
'azimuth_of_central_line': 9.02638777018478,
'false_easting': 0.,
'false_northing': 0.,
'gamma': 0,
'geographic_crs_name': "unknown",
'grid_mapping_name': "oblique_mercator",
'horizontal_datum_name': "unknown",
'latitude_of_projection_origin': -0.256794486098476,
'longitude_of_projection_origin': 13.7888658224205,
'prime_meridian_name': "Greenwich",
'reference_ellipsoid_name': "WGS84"}
omerc_expected = xr.DataArray(data=0, attrs=omerc_dict)

ds = ds_base.copy()
ds.attrs['area'] = area
res, grid_mapping = area2gridmapping(ds)

self.assertEqual(res.attrs['grid_mapping'], 'omerc')
_gm_matches(grid_mapping, omerc_expected)

def test_area2lonlat(self):
"""Test the conversion from areas to lon/lat."""
Expand Down
21 changes: 10 additions & 11 deletions satpy/writers/cf_writer.py
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Original file line number Diff line number Diff line change
Expand Up @@ -142,15 +142,10 @@
def tmerc2cf(area):
"""Return the cf grid mapping for the tmerc projection."""
proj_dict = area.proj_dict
args = dict(azimuth_of_central_line=proj_dict.get('alpha'),
latitude_of_projection_origin=proj_dict.get('lat_0'),
longitude_of_projection_origin=proj_dict.get('lon_0'),
latitude_of_meridian_ts=proj_dict.get('lat_ts'),
args = dict(latitude_of_projection_origin=proj_dict.get('lat_0'),
longitude_of_central_meridian=proj_dict.get('lon_0'),
grid_mapping_name='transverse_mercator',
reference_ellipsoid_name=proj_dict.get('ellps', 'WGS84'),
prime_meridian_name=proj_dict.get('pm', 'Greenwich'),
horizontal_datum_name=proj_dict.get('datum', 'unknown'),
geographic_crs_name='unknown',
false_easting=0.,
false_northing=0.
)
Expand Down Expand Up @@ -185,13 +180,17 @@ def omerc2cf(area):

def geos2cf(area):
"""Return the cf grid mapping for the geos projection."""
from pyresample.utils import proj4_radius_parameters
proj_dict = area.proj_dict
a, b = proj4_radius_parameters(proj_dict)
args = dict(perspective_point_height=proj_dict.get('h'),
latitude_of_projection_origin=proj_dict.get('lat_0'),
longitude_of_projection_origin=proj_dict.get('lon_0'),
latitude_of_projection_origin=proj_dict.get('lat_0', 0),
longitude_of_projection_origin=proj_dict.get('lon_0', 0),
grid_mapping_name='geostationary',
semi_major_axis=proj_dict.get('a'),
semi_minor_axis=proj_dict.get('b'),
semi_major_axis=a,
semi_minor_axis=b,
# semi_major_axis=proj_dict.get('a'),
# semi_minor_axis=proj_dict.get('b'),
sweep_axis=proj_dict.get('sweep'),
)
return args
Expand Down