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# (C) British Crown Copyright 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/>.
"""
Tests for the Gnomonic coordinate system.
"""
from __future__ import (absolute_import, division, print_function)
import numpy as np
from numpy.testing import assert_almost_equal
import pytest
import cartopy.crs as ccrs
from .helpers import check_proj_params
def test_default():
gnom = ccrs.Gnomonic()
other_args = {'a=6378137.0', 'lon_0=0.0', 'lat_0=0.0'}
check_proj_params('gnom', gnom, other_args)
assert_almost_equal(np.array(gnom.x_limits),
[-5e7, 5e7])
assert_almost_equal(np.array(gnom.y_limits),
[-5e7, 5e7])
def test_sphere_globe():
globe = ccrs.Globe(semimajor_axis=1000, ellipse=None)
gnom = ccrs.Gnomonic(globe=globe)
other_args = {'a=1000', 'lon_0=0.0', 'lat_0=0.0'}
check_proj_params('gnom', gnom, other_args)
assert_almost_equal(gnom.x_limits, [-5e7, 5e7])
assert_almost_equal(gnom.y_limits, [-5e7, 5e7])
def test_ellipse_globe():
globe = ccrs.Globe(ellipse='WGS84')
with pytest.warns(UserWarning,
match='does not handle elliptical globes.') as w:
gnom = ccrs.Gnomonic(globe=globe)
assert len(w) == 1
other_args = {'ellps=WGS84', 'lon_0=0.0', 'lat_0=0.0'}
check_proj_params('gnom', gnom, other_args)
# Limits are the same as default since ellipses are not supported.
assert_almost_equal(gnom.x_limits, [-5e7, 5e7])
assert_almost_equal(gnom.y_limits, [-5e7, 5e7])
def test_eccentric_globe():
globe = ccrs.Globe(semimajor_axis=1000, semiminor_axis=500,
ellipse=None)
with pytest.warns(UserWarning,
match='does not handle elliptical globes.') as w:
gnom = ccrs.Gnomonic(globe=globe)
assert len(w) == 1
other_args = {'a=1000', 'b=500', 'lon_0=0.0', 'lat_0=0.0'}
check_proj_params('gnom', gnom, other_args)
# Limits are the same as spheres since ellipses are not supported.
assert_almost_equal(gnom.x_limits, [-5e7, 5e7])
assert_almost_equal(gnom.y_limits, [-5e7, 5e7])
@pytest.mark.parametrize('lat', [-10, 0, 10])
@pytest.mark.parametrize('lon', [-10, 0, 10])
def test_central_params(lat, lon):
gnom = ccrs.Gnomonic(central_latitude=lat, central_longitude=lon)
other_args = {'lat_0={}'.format(lat), 'lon_0={}'.format(lon),
'a=6378137.0'}
check_proj_params('gnom', gnom, other_args)
assert_almost_equal(np.array(gnom.x_limits),
[-5e7, 5e7])
assert_almost_equal(np.array(gnom.y_limits),
[-5e7, 5e7])
def test_grid():
# USGS Professional Paper 1395, pg 168, Table 26
globe = ccrs.Globe(ellipse=None,
semimajor_axis=1.0, semiminor_axis=1.0)
gnom = ccrs.Gnomonic(globe=globe)
geodetic = gnom.as_geodetic()
other_args = {'a=1.0', 'b=1.0', 'lon_0=0.0', 'lat_0=0.0'}
check_proj_params('gnom', gnom, other_args)
assert_almost_equal(np.array(gnom.x_limits),
[-5e7, 5e7])
assert_almost_equal(np.array(gnom.y_limits),
[-5e7, 5e7])
lats, lons = np.mgrid[0:90:10, 0:90:10].reshape((2, -1))
expected_x = np.tile(
[0.0000, 0.1763, 0.3640, 0.5774, 0.8391, 1.1918, 1.7321, 2.7475,
5.6713],
9)
expected_y = np.array([
[5.6713, 2.7475, 1.7321, 1.1918, 0.8391, 0.5774, 0.3640, 0.1763, 0],
[5.7588, 2.7899, 1.7588, 1.2101, 0.8520, 0.5863, 0.3696, 0.1790, 0],
[6.0353, 2.9238, 1.8432, 1.2682, 0.8930, 0.6144, 0.3873, 0.1876, 0],
[6.5486, 3.1725, 2.0000, 1.3761, 0.9689, 0.6667, 0.4203, 0.2036, 0],
[7.4033, 3.5866, 2.2610, 1.5557, 1.0954, 0.7537, 0.4751, 0.2302, 0],
[8.8229, 4.2743, 2.6946, 1.8540, 1.3054, 0.8982, 0.5662, 0.2743, 0],
[11.3426, 5.4950, 3.4641, 2.3835, 1.6782, 1.1547, 0.7279, 0.3527, 0],
[16.5817, 8.0331, 5.0642, 3.4845, 2.4534, 1.6881, 1.0642, 0.5155, 0],
[32.6596, 15.8221, 9.9745, 6.8630, 4.8322, 3.3248, 2.0960, 1.0154, 0],
])[:, ::-1].T.ravel()
# Test all quadrants; they are symmetrical.
for lon_sign in [1, -1]:
for lat_sign in [1, -1]:
result = gnom.transform_points(geodetic,
lon_sign * lons, lat_sign * lats)
assert_almost_equal(result[:, 0], lon_sign * expected_x, decimal=4)
assert_almost_equal(result[:, 1], lat_sign * expected_y, decimal=4)
def test_sphere_transform():
# USGS Professional Paper 1395, pp 319 - 320
globe = ccrs.Globe(semimajor_axis=1.0, semiminor_axis=1.0,
ellipse=None)
gnom = ccrs.Gnomonic(central_latitude=40.0, central_longitude=-100.0,
globe=globe)
geodetic = gnom.as_geodetic()
other_args = {'a=1.0', 'b=1.0', 'lon_0=-100.0', 'lat_0=40.0'}
check_proj_params('gnom', gnom, other_args)
assert_almost_equal(np.array(gnom.x_limits),
[-5e7, 5e7])
assert_almost_equal(np.array(gnom.y_limits),
[-5e7, 5e7])
result = gnom.transform_point(-110.0, 30.0, geodetic)
assert_almost_equal(result, np.array([-0.1542826, -0.1694739]))
inverse_result = geodetic.transform_point(result[0], result[1], gnom)
assert_almost_equal(inverse_result, [-110.0, 30.0])
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