def get_convex_hull(self):
"""
Get a convex polygon object that contains projections of all the points
of the mesh.
:returns:
Instance of :class:`nhlib.geo.polygon.Polygon` that is a convex
hull around all the points in this mesh. If the original mesh
had only one point, the resulting polygon has a square shape
with a side length of 10 meters. If there were only two points,
resulting polygon is a stripe 10 meters wide.
"""
# avoid circular imports
from nhlib.geo.polygon import Polygon
# create a projection centered in the center of points collection
proj = geo_utils.get_orthographic_projection(
*geo_utils.get_spherical_bounding_box(self.lons, self.lats)
)
# project all the points and create a shapely multipoint object.
# need to copy an array because otherwise shapely misinterprets it
coords = numpy.transpose(proj(self.lons, self.lats)).copy()
multipoint = shapely.geometry.MultiPoint(coords)
# create a 2d polygon from a convex hull around that multipoint
polygon2d = multipoint.convex_hull
# if mesh had only one point, the convex hull is a point. if there
# were two, it is a line string. we need to return a convex polygon
# object, so extend that area-less geometries by some arbitrarily
# small distance, like five meters.
if isinstance(polygon2d, (shapely.geometry.LineString,
shapely.geometry.Point)):
polygon2d = polygon2d.buffer(0.005, 1)
return Polygon._from_2d(polygon2d, proj)
def to_polygon(self, radius):
"""
Create a circular polygon with specified radius centered in the point.
:param radius:
Required radius of a new polygon, in km.
:returns:
Instance of :class:`~nhlib.geo.polygon.Polygon` that approximates
a circle around the point with specified radius.
"""
assert radius > 0
# avoid circular imports
from nhlib.geo.polygon import Polygon
# get a projection that is centered in the point
proj = geo_utils.get_orthographic_projection(
self.longitude, self.longitude, self.latitude, self.latitude
)
# create a shapely object from a projected point coordinates,
# which are supposedly (0, 0)
point = shapely.geometry.Point(*proj(self.longitude, self.latitude))
# extend the point to a shapely polygon using buffer()
# and create nhlib.geo.polygon.Polygon object from it
return Polygon._from_2d(point.buffer(radius), proj)
def to_polygon(self, radius):
"""
Create a circular polygon with specified radius centered in the point.
:param radius:
Required radius of a new polygon, in km.
:returns:
Instance of :class:`~nhlib.geo.polygon.Polygon` that approximates
a circle around the point with specified radius.
"""
assert radius > 0
# avoid circular imports
from nhlib.geo.polygon import Polygon
# get a projection that is centered in the point
proj = geo_utils.get_orthographic_projection(self.longitude,
self.longitude,
self.latitude,
self.latitude)
# create a shapely object from a projected point coordinates,
# which are supposedly (0, 0)
point = shapely.geometry.Point(*proj(self.longitude, self.latitude))
# extend the point to a shapely polygon using buffer()
# and create nhlib.geo.polygon.Polygon object from it
return Polygon._from_2d(point.buffer(radius), proj)
def get_convex_hull(self):
"""
Get a convex polygon object that contains projections of all the points
of the mesh.
:returns:
Instance of :class:`nhlib.geo.polygon.Polygon` that is a convex
hull around all the points in this mesh. If the original mesh
had only one point, the resulting polygon has a square shape
with a side length of 10 meters. If there were only two points,
resulting polygon is a stripe 10 meters wide.
"""
proj, polygon2d = self._get_proj_convex_hull()
# if mesh had only one point, the convex hull is a point. if there
# were two, it is a line string. we need to return a convex polygon
# object, so extend that area-less geometries by some arbitrarily
# small distance.
if isinstance(polygon2d, (shapely.geometry.LineString,
shapely.geometry.Point)):
polygon2d = polygon2d.buffer(self.DIST_TOLERANCE, 1)
# avoid circular imports
from nhlib.geo.polygon import Polygon
return Polygon._from_2d(polygon2d, proj)
def get_convex_hull(self):
"""
Get a convex polygon object that contains projections of all the points
of the mesh.
:returns:
Instance of :class:`nhlib.geo.polygon.Polygon` that is a convex
hull around all the points in this mesh. If the original mesh
had only one point, the resulting polygon has a square shape
with a side length of 10 meters. If there were only two points,
resulting polygon is a stripe 10 meters wide.
"""
proj, polygon2d = self._get_proj_convex_hull()
# if mesh had only one point, the convex hull is a point. if there
# were two, it is a line string. we need to return a convex polygon
# object, so extend that area-less geometries by some arbitrarily
# small distance.
if isinstance(polygon2d,
(shapely.geometry.LineString, shapely.geometry.Point)):
polygon2d = polygon2d.buffer(self.DIST_TOLERANCE, 1)
# avoid circular imports
from nhlib.geo.polygon import Polygon
return Polygon._from_2d(polygon2d, proj)
