def test_polygon_on_international_date_line(self):
MESH_SPACING = 10
bl = geo.Point(177, 40)
bml = geo.Point(179, 40)
bmr = geo.Point(-179, 40)
br = geo.Point(-177, 40)
tr = geo.Point(-177, 43)
tmr = geo.Point(-179, 43)
tml = geo.Point(179, 43)
tl = geo.Point(177, 43)
poly = geo.Polygon([bl, bml, bmr, br, tr, tmr, tml, tl])
mesh = list(poly.discretize(mesh_spacing=MESH_SPACING))
west = east = mesh[0]
for point in mesh:
if geo_utils.get_longitudinal_extent(point.longitude,
west.longitude) > 0:
west = point
if geo_utils.get_longitudinal_extent(point.longitude,
east.longitude) < 0:
east = point
self.assertLess(west.longitude, 177.15)
self.assertGreater(east.longitude, -177.15)
def discretize(self, mesh_spacing):
"""
Get a mesh of uniformly spaced points inside the polygon area
with distance of ``mesh_spacing`` km between.
:returns:
An instance of :class:`~nhlib.geo.mesh.Mesh` that holds
the points data. Mesh is created with no depth information
(all the points are on the Earth surface).
"""
self._init_polygon2d()
west, east, north, south = self._bbox
lons = []
lats = []
# we cover the bounding box (in spherical coordinates) from highest
# to lowest latitude and from left to right by longitude. we step
# by mesh spacing distance (linear measure). we check each point
# if it is inside the polygon and yield the point object, if so.
# this way we produce an uniformly-spaced mesh regardless of the
# latitude.
latitude = north
while latitude > south:
longitude = west
while utils.get_longitudinal_extent(longitude, east) > 0:
# we use Cartesian space just for checking if a point
# is inside of the polygon.
x, y = self._projection(longitude, latitude)
if self._polygon2d.contains(shapely.geometry.Point(x, y)):
lons.append(longitude)
lats.append(latitude)
# move by mesh spacing along parallel...
longitude, _, = geodetic.point_at(longitude, latitude,
90, mesh_spacing)
# ... and by the same distance along meridian in outer one
_, latitude = geodetic.point_at(west, latitude, 180, mesh_spacing)
lons = numpy.array(lons)
lats = numpy.array(lats)
return Mesh(lons, lats, depths=None)
def test_international_date_line(self):
self.assertEqual(utils.get_longitudinal_extent(-178.3, 177.7), -4)
self.assertEqual(utils.get_longitudinal_extent(177.7, -178.3), 4)
self.assertEqual(utils.get_longitudinal_extent(95, -180 + 94), 179)
self.assertEqual(utils.get_longitudinal_extent(95, -180 + 96), -179)
def test_negative(self):
self.assertEqual(utils.get_longitudinal_extent(20, 10), -10)
self.assertEqual(utils.get_longitudinal_extent(-10, -15), -5)
def test_positive(self):
self.assertEqual(utils.get_longitudinal_extent(10, 20), 10)
self.assertEqual(utils.get_longitudinal_extent(-120, 30), 150)
