Interpret inverse_flattening = 0 as spherical datum in mapping.py #1920
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src/metpy/plots/mapping.py
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| if kwargs.get('inverse_flattening', None) == 0: | ||
| kwargs['ellipse'] = 'sphere' | ||
| kwargs.pop('inverse_flattening', None) | ||
| # WGS84 with semi_major==semi_minor is NOT the same as spherical Earth | ||
| # Also need to handle the case where we're not given any spheroid | ||
| kwargs['ellipse'] = None if kwargs else 'sphere' |
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Ok, this is the source of the current test failure. You should move this line (and it's comment) up to line 63 (in the else) to have it say:
# Override CartoPy's default ellipse setting depending on whether we have any metadata to map about the
# spheroid.
kwargs['ellipse'] = None if kwargs else 'sphere'
dopplershift
requested changes
Jun 25, 2021
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Code changes generally look in good shape. Can you add a test that validates that we're doing what we want? We have this right now for testing the globe:
def test_globe():
"""Test handling building a cartopy globe."""
attrs = {'grid_mapping_name': 'lambert_conformal_conic', 'earth_radius': 6367000,
'standard_parallel': 25}
proj = CFProjection(attrs)
crs = proj.to_cartopy()
globe_params = crs.globe.to_proj4_params()
assert globe_params['ellps'] == 'sphere'
assert globe_params['a'] == 6367000
assert globe_params['b'] == 6367000It would be good to write a new test function in test_mapping.py that sets inverse_flattening to 0 and verifies that we can do what was failing in the original issue.
| @@ -49,16 +49,23 @@ def cartopy_globe(self): | |||
| if 'earth_radius' in self._attrs: | |||
| kwargs = {'ellipse': 'sphere', 'semimajor_axis': self._attrs['earth_radius'], | |||
| 'semiminor_axis': self._attrs['earth_radius']} | |||
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Looks like a stray change crept in here.
dopplershift
requested changes
Jun 30, 2021
dopplershift
added
Area: Projections
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Currently, pyproj CF output is not accepted by metpy.assign_crs(). The relevant logic in in /metpy/plot/mapping.py, property cartopy_globe. The error is occuring because the conversion from PyProj to CF produces a value of 0 for inverse_flattening.
This PR updates mapping.py to not pass on a value of 0 for inverse_flattening by interpreting it as a spherical datum. Currently, it passes all tests except for test_globe_spheroid() in test_mapping.py.