spacepy.coordinates.Coords

class spacepy.coordinates.Coords(data, dtype, carsph[, units, ticks, use_irbem])

A class holding spatial coordinates and enabling transformation between coordinate systems. Coordinates can be stored as Cartesian or spherical and units are assumed to be Re (distance) and degrees (angle)

Note

Although other units may be specified and will be carried through, most functions throughout SpacePy assume distances in Re and angles in degrees, regardless of specified units.

By default, coordinate transforms are based on the SpacePy library’s high-accuracy coordinates backend. The legacy transforms provided by the IRBEM library can also be used by setting the use_irbem flag to True; its manual <http://svn.code.sf.net/p/irbem/code/trunk/manual/user_guide.html>`_ may prove useful. For a good reference on heliospheric and magnetospheric coordinate systems, see Franz & Harper, “Heliospheric Coordinate Systems”, Planet. Space Sci., 50, pp 217-233, 2002 (https://doi.org/10.1016/S0032-0633(01)00119-2).

Parameters:

datalist or ndarray, dim = (n,3)

coordinate points [X,Y,Z] or [rad, lat, lon]

dtypestring

coordinate system; supported systems are defined in module-level documentation. Common systems include GEO, GSE, GSM, SM, MAG, ECIMOD

carsphstring

Cartesian or spherical, ‘car’ or ‘sph’

unitslist of strings, optional

standard are [‘Re’, ‘Re’, ‘Re’] or [‘Re’, ‘deg’, ‘deg’] depending on the carsph content. See note.

ticksTicktock instance, optional

used for coordinate transformations (see a.convert)

use_irbembool

Added in version 0.3.0.

Set to True to use IRBEM for coordinate transforms. Otherwise use SpacePy’s coordinate transform library.

Returns:

outCoords instance

instance with a.data, a.carsph, etc.

See also

spacepy.coordinates.DEFAULTS

spacepy.time.Ticktock

Examples

>>> from spacepy import coordinates as coord
>>> cvals = coord.Coords([[1,2,4],[1,2,2]], 'GEO', 'car')
>>> cvals.x  # returns all x coordinates
array([1, 1])
>>> from spacepy.time import Ticktock
>>> cvals.ticks = Ticktock(['2002-02-02T12:00:00', '2002-02-02T12:00:00'], 'ISO') # add ticks
>>> newcoord = cvals.convert('GSM', 'sph')
>>> newcoord

__init__(data, dtype, carsph, units=None, ticks=None, use_irbem=None)

Methods

append(other)	Append another Coords instance to the current one
convert(returntype, returncarsph)	Create a new Coords instance with new coordinate types
from_skycoord(skycoord[, use_irbem])	Create a Coords instance from an Astropy SkyCoord instance
to_skycoord()	Create an Astropy SkyCoord instance based on this instance

append(other)

Append another Coords instance to the current one

Parameters:

otherCoords instance

Coords instance to append

convert(returntype, returncarsph)

Create a new Coords instance with new coordinate types

Parameters:

returntypestring

coordinate system, see module level documentation for supported systems

returncarsphstring

coordinate type, possible ‘car’ for Cartesian and ‘sph’ for spherical

Returns:

outCoords object

Coords object in the new coordinate system

Examples

>>> from spacepy.coordinates import Coords
>>> y = Coords([[1,2,4],[1,2,2]], 'GEO', 'car')
>>> from spacepy.time import Ticktock
>>> y.ticks = Ticktock(['2002-02-02T12:00:00', '2002-02-02T12:00:00'], 'ISO')
>>> x = y.convert('SM','car')
>>> x
Coords( [[ 0.81134097  2.6493305   3.6500375 ]
 [ 0.92060408  2.30678864  1.68262126]] ), dtype=SM,car, units=['Re', 'Re', 'Re']

classmethod from_skycoord(skycoord, use_irbem=None)

Create a Coords instance from an Astropy SkyCoord instance

Parameters:

skycoordastropy.coordinates.SkyCoord

The coordinate to be converted

Returns:

outCoords instance

The converted coordinate

Notes

This method requires Astropy to be installed.

This method uses the GEO coordinate frame as the common frame between the two libraries.

to_skycoord()

Create an Astropy SkyCoord instance based on this instance

Returns:

outastropy.coordinates.SkyCoord

This coordinate as an Astropy SkyCoord

Notes

This method requires Astropy to be installed.

This method uses the GEO coordinate frame as the common frame between the two libraries.