def intersection(self, path):
"""
Return the intersection between the paths
Parameters
----------
path: GeoPath object
path to intersect
Returns
-------
point: GeoPoint
point of intersection between paths
"""
frame = self.positionA.frame
n_EA1_E, n_EA2_E = self.nvector_normals()
n_EB1_E, n_EB2_E = path.nvector_normals()
# Find the intersection between the two paths, n_EC_E:
n_EC_E_tmp = unit(cross(cross(n_EA1_E, n_EA2_E, axis=0),
cross(n_EB1_E, n_EB2_E, axis=0), axis=0),
norm_zero_vector=np.nan)
# n_EC_E_tmp is one of two solutions, the other is -n_EC_E_tmp. Select
# the one that is closet to n_EA1_E, by selecting sign from the dot
# product between n_EC_E_tmp and n_EA1_E:
n_EC_E = np.sign(dot(n_EC_E_tmp.T, n_EA1_E)) * n_EC_E_tmp
if np.any(np.isnan(n_EC_E)):
warnings.warn('Paths are Equal. Intersection point undefined. '
'NaN returned.')
lat_EC, long_EC = n_E2lat_lon(n_EC_E, frame.R_Ee)
return GeoPoint(lat_EC, long_EC, frame=frame)
def cross_track_distance(self, point, method='greatcircle', radius=None):
"""
Return cross track distance from the path to a point.
Parameters
----------
point: GeoPoint, Nvector or ECEFvector object
position to measure the cross track distance to.
radius: real scalar
radius of sphere in [m]. Default mean Earth radius
method: string
defining distance calculated. Options are:
'greatcircle' or 'euclidean'
Returns
-------
distance: real scalar
distance in [m]
"""
if radius is None:
radius = self._get_average_radius()
c_E = unit(self._normal_to_great_circle())
n_EB_E = point.to_nvector()
cos_angle = dot(c_E.T, n_EB_E.normal)
if method[0].lower() == 'e':
return self._euclidean_cross_track_distance(cos_angle, radius)
return self._great_circle_cross_track_distance(cos_angle, radius)
def _cross_track_point(path, point):
"""Extend nvector package to find the projection point.
The projection point is the closest point on path to the given point.
Based on the nvector.cross_track_distance function.
http://www.navlab.net/nvector/
:param path: GeoPath
:param point: GeoPoint
"""
c_E = great_circle_normal(*path.nvector_normals())
n_EB_E = point.to_nvector().normal # type: np.array
c_EP_E = np.cross(c_E, n_EB_E, axis=0)
# Find intersection point C that is closest to point B
frame = path.positionA.frame
n_EA1_E = path.positionA.to_nvector(
).normal # should also be ok to use n_EB_C
n_EC_E_tmp = unit(np.cross(c_E, c_EP_E, axis=0), norm_zero_vector=np.nan)
n_EC_E = np.sign(np.dot(n_EC_E_tmp.T, n_EA1_E)) * n_EC_E_tmp
if np.any(np.isnan(n_EC_E)):
raise Exception(
'Paths are Equal. Intersection point undefined. NaN returned.')
lat_C, long_C = n_E2lat_lon(n_EC_E, frame.R_Ee)
return nv.GeoPoint(lat_C, long_C, frame=frame)
def interpolate(self, ti):
"""
Return the interpolated point along the path
Parameters
----------
ti: real scalar
interpolation time assuming position A and B is at t0=0 and t1=1,
respectively.
Returns
-------
point: Nvector
point of interpolation along path
"""
point_a, point_b = self.nvectors()
point_c = point_a + (point_b - point_a) * ti
point_c.normal = unit(point_c.normal, norm_zero_vector=np.nan)
return point_c
def interpolate(self, ti):
"""
Return the interpolated point along the path
Parameters
----------
ti: real scalar
interpolation time assuming position A and B is at t0=0 and t1=1,
respectively.
Returns
-------
point: Nvector
point of interpolation along path
"""
n_EB_E_t0, n_EB_E_t1 = self.nvector_normals()
n_EB_E_ti = unit(n_EB_E_t0 + ti * (n_EB_E_t1 - n_EB_E_t0))
zi = self.positionA.z + ti * (self.positionB.z-self.positionA.z)
frame = self.positionA.frame
return frame.Nvector(n_EB_E_ti, zi)
def unit(self):
"""Normalizes self to unit vector(s)"""
self.normal = unit(self.normal)
