UnitSphericalRepresentation¶

class
astropy.coordinates.
UnitSphericalRepresentation
(lon, lat=None, differentials=None, copy=True)[source]¶ Bases:
astropy.coordinates.BaseRepresentation
Representation of points on a unit sphere.
 Parameters
 lon, lat
Quantity
[:ref: ‘angle’] orstr
The longitude and latitude of the point(s), in angular units. The latitude should be between 90 and 90 degrees, and the longitude will be wrapped to an angle between 0 and 360 degrees. These can also be instances of
Angle
,Longitude
, orLatitude
. differentials
dict
,BaseDifferential
, optional Any differential classes that should be associated with this representation. The input must either be a single
BaseDifferential
instance (see_compatible_differentials
for valid types), or a dictionary of of differential instances with keys set to a string representation of the SI unit with which the differential (derivative) is taken. For example, for a velocity differential on a positional representation, the key would be's'
for seconds, indicating that the derivative is a time derivative. copybool, optional
If
True
(default), arrays will be copied. IfFalse
, arrays will be references, though possibly broadcast to ensure matching shapes.
 lon, lat
Attributes Summary
The latitude of the point(s).
The longitude of the point(s).
Methods Summary
cross
(other)Cross product of two representations.
from_cartesian
(cart)Converts 3D rectangular cartesian coordinates to spherical polar coordinates.
mean
(*args, **kwargs)Vector mean.
norm
()Vector norm.
represent_as
(other_class[, differential_class])Convert coordinates to another representation.
scale_factors
([omit_coslat])Scale factors for each component’s direction.
sum
(*args, **kwargs)Vector sum.
Converts spherical polar coordinates to 3D rectangular cartesian coordinates.
transform
(matrix)Transform the unitspherical coordinates using a 3x3 matrix.
Cartesian unit vectors in the direction of each component.
Attributes Documentation

attr_classes
= {'lat': <class 'astropy.coordinates.angles.Latitude'>, 'lon': <class 'astropy.coordinates.angles.Longitude'>}¶

lat
¶ The latitude of the point(s).

lon
¶ The longitude of the point(s).
Methods Documentation

cross
(other)[source]¶ Cross product of two representations.
The calculation is done by converting both
self
andother
toCartesianRepresentation
, and converting the result back toSphericalRepresentation
. Parameters
 other
BaseRepresentation
subclass instance The representation to take the cross product with.
 other
 Returns
 cross_product
SphericalRepresentation
With vectors perpendicular to both
self
andother
.
 cross_product

classmethod
from_cartesian
(cart)[source]¶ Converts 3D rectangular cartesian coordinates to spherical polar coordinates.

mean
(*args, **kwargs)[source]¶ Vector mean.
The representation is converted to cartesian, the means of the x, y, and z components are calculated, and the result is converted to a
SphericalRepresentation
.Refer to
mean
for full documentation of the arguments, noting thataxis
is the entry in theshape
of the representation, and that theout
argument cannot be used.

norm
()[source]¶ Vector norm.
The norm is the standard Frobenius norm, i.e., the square root of the sum of the squares of all components with nonangular units, which is always unity for vectors on the unit sphere.
 Returns
 norm
Quantity
[:ref: ‘dimensionless’] Dimensionless ones, with the same shape as the representation.
 norm

represent_as
(other_class, differential_class=None)[source]¶ Convert coordinates to another representation.
If the instance is of the requested class, it is returned unmodified. By default, conversion is done via Cartesian coordinates. Also note that orientation information at the origin is not preserved by conversions through Cartesian coordinates. See the docstring for
to_cartesian()
for an example. Parameters
 other_class
BaseRepresentation
subclass The type of representation to turn the coordinates into.
 differential_class
dict
ofBaseDifferential
, optional Classes in which the differentials should be represented. Can be a single class if only a single differential is attached, otherwise it should be a
dict
keyed by the same keys as the differentials.
 other_class

scale_factors
(omit_coslat=False)[source]¶ Scale factors for each component’s direction.
Given unit vectors \(\hat{e}_c\) and scale factors \(f_c\), a change in one component of \(\delta c\) corresponds to a change in representation of \(\delta c \times f_c \times \hat{e}_c\).

sum
(*args, **kwargs)[source]¶ Vector sum.
The representation is converted to cartesian, the sums of the x, y, and z components are calculated, and the result is converted to a
SphericalRepresentation
.Refer to
sum
for full documentation of the arguments, noting thataxis
is the entry in theshape
of the representation, and that theout
argument cannot be used.

to_cartesian
()[source]¶ Converts spherical polar coordinates to 3D rectangular cartesian coordinates.

transform
(matrix)[source]¶ Transform the unitspherical coordinates using a 3x3 matrix.
This returns a new representation and does not modify the original one. Any differentials attached to this representation will also be transformed.
 Parameters
 matrix(3,3) array_like
A 3x3 matrix, such as a rotation matrix (or a stack of matrices).
 Returns
UnitSphericalRepresentation
orSphericalRepresentation
If
matrix
is O(3) – \(M \dot M^T = I\) – like a rotation, then the result is aUnitSphericalRepresentation
. All other matrices will change the distance, so the dimensional representation is used instead.

unit_vectors
()[source]¶ Cartesian unit vectors in the direction of each component.
Given unit vectors \(\hat{e}_c\) and scale factors \(f_c\), a change in one component of \(\delta c\) corresponds to a change in representation of \(\delta c \times f_c \times \hat{e}_c\).
 Returns
 unit_vectors
dict
ofCartesianRepresentation
The keys are the component names.
 unit_vectors