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# (C) British Crown Copyright 2013 - 2018, Met Office
#
# This file is part of cartopy.
#
# cartopy is free software: you can redistribute it and/or modify it under
# the terms of the GNU Lesser General Public License as published by the
# Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# cartopy is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with cartopy. If not, see <https://www.gnu.org/licenses/>.
from __future__ import (absolute_import, division, print_function)
import numpy as np
from numpy.testing import assert_almost_equal
import cartopy.crs as ccrs
from .helpers import check_proj_params
class TestStereographic(object):
def test_default(self):
stereo = ccrs.Stereographic()
other_args = {'ellps=WGS84', 'lat_0=0.0', 'lon_0=0.0', 'x_0=0.0',
'y_0=0.0'}
check_proj_params('stere', stereo, other_args)
assert_almost_equal(np.array(stereo.x_limits),
[-5e7, 5e7], decimal=4)
assert_almost_equal(np.array(stereo.y_limits),
[-5e7, 5e7], decimal=4)
def test_eccentric_globe(self):
globe = ccrs.Globe(semimajor_axis=1000, semiminor_axis=500,
ellipse=None)
stereo = ccrs.Stereographic(globe=globe)
other_args = {'a=1000', 'b=500', 'lat_0=0.0', 'lon_0=0.0', 'x_0=0.0',
'y_0=0.0'}
check_proj_params('stere', stereo, other_args)
# The limits in this test are sensible values, but are by no means
# a "correct" answer - they mean that plotting the crs results in a
# reasonable map.
assert_almost_equal(np.array(stereo.x_limits),
[-7839.27971444, 7839.27971444], decimal=4)
assert_almost_equal(np.array(stereo.y_limits),
[-3932.82587779, 3932.82587779], decimal=4)
def test_true_scale(self):
# The "true_scale_latitude" parameter only makes sense for
# polar stereographic projections (#339 and #455).
# For now only the proj string creation is tested
# See test_scale_factor for test on projection.
globe = ccrs.Globe(ellipse='sphere')
stereo = ccrs.NorthPolarStereo(true_scale_latitude=30, globe=globe)
other_args = {'ellps=sphere', 'lat_0=90', 'lon_0=0.0', 'lat_ts=30',
'x_0=0.0', 'y_0=0.0'}
check_proj_params('stere', stereo, other_args)
def test_scale_factor(self):
# See #455
# Use spherical Earth in North Polar Stereographic to check
# equivalence between true_scale and scale_factor.
# In these conditions a scale factor of 0.75 corresponds exactly to
# a standard parallel of 30N.
globe = ccrs.Globe(ellipse='sphere')
stereo = ccrs.Stereographic(central_latitude=90., scale_factor=0.75,
globe=globe)
other_args = {'ellps=sphere', 'lat_0=90.0', 'lon_0=0.0', 'k_0=0.75',
'x_0=0.0', 'y_0=0.0'}
check_proj_params('stere', stereo, other_args)
# Now test projections
lon, lat = 10, 10
projected_scale_factor = stereo.transform_point(lon, lat,
ccrs.Geodetic())
# should be equivalent to North Polar Stereo with
# true_scale_latitude = 30
nstereo = ccrs.NorthPolarStereo(globe=globe, true_scale_latitude=30)
projected_true_scale = nstereo.transform_point(lon, lat,
ccrs.Geodetic())
assert projected_true_scale == projected_scale_factor
def test_eastings(self):
stereo = ccrs.Stereographic()
stereo_offset = ccrs.Stereographic(false_easting=1234,
false_northing=-4321)
other_args = {'ellps=WGS84', 'lat_0=0.0', 'lon_0=0.0', 'x_0=1234',
'y_0=-4321'}
check_proj_params('stere', stereo_offset, other_args)
assert (tuple(np.array(stereo.x_limits) + 1234) ==
stereo_offset.x_limits)
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