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# Copyright Crown and Cartopy Contributors
#
# This file is part of Cartopy and is released under the BSD 3-clause license.
# See LICENSE in the root of the repository for full licensing details.
import warnings
import numpy as np
from numpy.testing import assert_array_almost_equal
import pytest
import cartopy.crs as ccrs
class TestTransformVectors:
def test_transform(self):
# Test some simple vectors to make sure they are transformed
# correctly.
rlons = np.array([-90., 0, 90., 180.])
rlats = np.array([0., 0., 0., 0.])
src_proj = ccrs.PlateCarree()
target_proj = ccrs.Stereographic(central_latitude=90,
central_longitude=0)
# transform grid eastward vectors
ut, vt = target_proj.transform_vectors(src_proj,
rlons,
rlats,
np.ones([4]),
np.zeros([4]))
assert_array_almost_equal(ut, np.array([0, 1, 0, -1]), decimal=2)
assert_array_almost_equal(vt, np.array([-1, 0, 1, 0]), decimal=2)
# transform grid northward vectors
ut, vt = target_proj.transform_vectors(src_proj,
rlons,
rlats,
np.zeros([4]),
np.ones([4]))
assert_array_almost_equal(ut, np.array([1, 0, -1, 0]), decimal=2)
assert_array_almost_equal(vt, np.array([0, 1, 0, -1]), decimal=2)
# transform grid north-eastward vectors
ut, vt = target_proj.transform_vectors(src_proj,
rlons,
rlats,
np.ones([4]),
np.ones([4]))
assert_array_almost_equal(ut, np.array([1, 1, -1, -1]), decimal=2)
assert_array_almost_equal(vt, np.array([-1, 1, 1, -1]), decimal=2)
def test_transform_and_inverse(self):
# Check a full circle transform back to the native projection.
x = np.arange(-60, 42.5, 2.5)
y = np.arange(30, 72.5, 2.5)
x2d, y2d = np.meshgrid(x, y)
u = np.cos(np.deg2rad(y2d))
v = np.cos(2. * np.deg2rad(x2d))
src_proj = ccrs.PlateCarree()
target_proj = ccrs.Stereographic(central_latitude=90,
central_longitude=0)
proj_xyz = target_proj.transform_points(src_proj, x2d, y2d)
xt, yt = proj_xyz[..., 0], proj_xyz[..., 1]
ut, vt = target_proj.transform_vectors(src_proj, x2d, y2d, u, v)
utt, vtt = src_proj.transform_vectors(target_proj, xt, yt, ut, vt)
assert_array_almost_equal(u, utt, decimal=4)
assert_array_almost_equal(v, vtt, decimal=4)
def test_invalid_input_domain(self):
# If an input coordinate is outside the input projection domain
# we should be able to handle it correctly.
rlon = np.array([270.])
rlat = np.array([0.])
u = np.array([1.])
v = np.array([0.])
src_proj = ccrs.PlateCarree()
target_proj = ccrs.Stereographic(central_latitude=90,
central_longitude=0)
ut, vt = target_proj.transform_vectors(src_proj, rlon, rlat, u, v)
assert_array_almost_equal(ut, np.array([0]), decimal=2)
assert_array_almost_equal(vt, np.array([-1]), decimal=2)
def test_invalid_x_domain(self):
# If the point we need to calculate the vector angle falls outside the
# source projection x-domain it should be handled correctly as long as
# it is not a corner point.
rlon = np.array([180.])
rlat = np.array([0.])
u = np.array([1.])
v = np.array([0.])
src_proj = ccrs.PlateCarree()
target_proj = ccrs.Stereographic(central_latitude=90,
central_longitude=0)
ut, vt = target_proj.transform_vectors(src_proj, rlon, rlat, u, v)
assert_array_almost_equal(ut, np.array([-1]), decimal=2)
assert_array_almost_equal(vt, np.array([0.]), decimal=2)
def test_invalid_y_domain(self):
# If the point we need to calculate the vector angle falls outside the
# source projection y-domain it should be handled correctly as long as
# it is not a corner point.
rlon = np.array([0.])
rlat = np.array([90.])
u = np.array([0.])
v = np.array([1.])
src_proj = ccrs.PlateCarree()
target_proj = ccrs.Stereographic(central_latitude=90,
central_longitude=0)
ut, vt = target_proj.transform_vectors(src_proj, rlon, rlat, u, v)
assert_array_almost_equal(ut, np.array([0.]), decimal=2)
assert_array_almost_equal(vt, np.array([1.]), decimal=2)
def test_invalid_xy_domain_corner(self):
# If the point we need to calculate the vector angle falls outside the
# source projection x and y-domain it should be handled correctly.
rlon = np.array([180.])
rlat = np.array([90.])
u = np.array([1.])
v = np.array([1.])
src_proj = ccrs.PlateCarree()
target_proj = ccrs.Stereographic(central_latitude=90,
central_longitude=0)
ut, vt = target_proj.transform_vectors(src_proj, rlon, rlat, u, v)
assert_array_almost_equal(ut, np.array([0.]), decimal=2)
assert_array_almost_equal(vt, np.array([-2**.5]), decimal=2)
def test_invalid_x_domain_corner(self):
# If the point we need to calculate the vector angle falls outside the
# source projection x-domain and is a corner point, it may be handled
# incorrectly and a warning should be raised.
rlon = np.array([180.])
rlat = np.array([90.])
u = np.array([1.])
v = np.array([-1.])
src_proj = ccrs.PlateCarree()
target_proj = ccrs.Stereographic(central_latitude=90,
central_longitude=0)
with pytest.warns(UserWarning):
warnings.simplefilter('always')
ut, vt = target_proj.transform_vectors(src_proj, rlon, rlat, u, v)
def test_invalid_y_domain_corner(self):
# If the point we need to calculate the vector angle falls outside the
# source projection y-domain and is a corner point, it may be handled
# incorrectly and a warning should be raised.
rlon = np.array([180.])
rlat = np.array([90.])
u = np.array([-1.])
v = np.array([1.])
src_proj = ccrs.PlateCarree()
target_proj = ccrs.Stereographic(central_latitude=90,
central_longitude=0)
with pytest.warns(UserWarning):
warnings.simplefilter('always')
ut, vt = target_proj.transform_vectors(src_proj, rlon, rlat, u, v)
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