Skip to main content
`Ctrl`+`K`

# PrecessedGeocentric

class astropy.coordinates.PrecessedGeocentric(*args, copy=True, representation_type=None, differential_type=None, **kwargs)

  Bases: `BaseRADecFrame`

  A coordinate frame defined in a similar manner as GCRS, but precessed to a requested (mean) equinox. Note that this does not end up the same as regular GCRS even for J2000 equinox, because the GCRS orientation is fixed to that of ICRS, which is not quite the same as the dynamical J2000 orientation.

  The frame attributes are listed under Other Parameters

  Parameters:
    data `BaseRepresentation` subclass instance

      A representation object or `None` to have no data (or use the coordinate component arguments, see below).

    ra `Angle`, optional, keyword-only

      The RA for this object (`dec` must also be given and `representation` must be None).

    dec `Angle`, optional, keyword-only

      The Declination for this object (`ra` must also be given and `representation` must be None).

    distance `Quantity` [:ref: ‘length’], optional, keyword-only

      The Distance for this object along the line-of-sight. (`representation` must be None).

    pm_ra_cosdec `Quantity` [:ref: ‘angular speed’], optional, keyword-only

      The proper motion in Right Ascension (including the `cos(dec)` factor) for this object (`pm_dec` must also be given).

    pm_dec `Quantity` [:ref: ‘angular speed’], optional, keyword-only

      The proper motion in Declination for this object (`pm_ra_cosdec` must also be given).

    radial_velocity `Quantity` [:ref: ‘speed’], optional, keyword-only

      The radial velocity of this object.

    representation_type `BaseRepresentation` subclass, `python:str`, optional

      A representation class or string name of a representation class. This sets the expected input representation class, thereby changing the expected keyword arguments for the data passed in. For example, passing `representation_type='cartesian'` will make the classes expect position data with cartesian names, i.e. `x, y, z` in most cases unless overridden via `frame_specific_representation_info`. To see this frame’s names, check out `<this frame>().representation_info`.

    differential_type `BaseDifferential` subclass, `python:str`, `python:dict`, optional

      A differential class or dictionary of differential classes (currently only a velocity differential with key ‘s’ is supported). This sets the expected input differential class, thereby changing the expected keyword arguments of the data passed in. For example, passing `differential_type='cartesian'` will make the classes expect velocity data with the argument names `v_x, v_y, v_z` unless overridden via `frame_specific_representation_info`. To see this frame’s names, check out `<this frame>().representation_info`.

    copy bool, optional

      If `True` (default), make copies of the input coordinate arrays. Can only be passed in as a keyword argument.

  Other Parameters:
    equinox `Time`

      The (mean) equinox to precess the coordinates to.

    obstime `Time`

      The time at which the observation is taken. Used for determining the position of the Earth.

    obsgeoloc `CartesianRepresentation`, `Quantity`

      The position of the observer relative to the center-of-mass of the Earth, oriented the same as BCRS/ICRS. Either [0, 0, 0], `CartesianRepresentation`, or proper input for one, i.e., a `Quantity` with shape (3, …) and length units. Defaults to [0, 0, 0], meaning “true” Geocentric.

    obsgeovel `CartesianRepresentation`, `Quantity`

      The velocity of the observer relative to the center-of-mass of the Earth, oriented the same as BCRS/ICRS. Either 0, `CartesianRepresentation`, or proper input for one, i.e., a `Quantity` with shape (3, …) and velocity units. Defaults to [0, 0, 0], meaning “true” Geocentric.

  Attributes Summary

  `default_differential` | Default representation for differential data (e.g., velocity)
  `default_representation` | Default representation for position data
  `equinox` | The equinox time
  `frame_attributes` |
  `frame_specific_representation_info` | Mapping for frame-specific component names
  `name` |
  `obsgeoloc` | The observer location relative to Earth center
  `obsgeovel` | The observer velocity relative to Earth center
  `obstime` | The reference time (e.g., time of observation)

  Attributes Documentation

  default_differential

    Default representation for differential data (e.g., velocity)

  default_representation

    Default representation for position data

  equinox

    The equinox time

    Default: J2000.000

  frame_attributes = {'equinox': <astropy.coordinates.attributes.TimeAttribute object>, 'obsgeoloc': <astropy.coordinates.attributes.CartesianRepresentationAttribute object>, 'obsgeovel': <astropy.coordinates.attributes.CartesianRepresentationAttribute object>, 'obstime': <astropy.coordinates.attributes.TimeAttribute object>}
  frame_specific_representation_info

    Mapping for frame-specific component names

  name = 'precessedgeocentric'
  obsgeoloc

    The observer location relative to Earth center

    Default: [0, 0, 0]

  obsgeovel

    The observer velocity relative to Earth center

    Default: [0, 0, 0]

  obstime

    The reference time (e.g., time of observation)

    Default: J2000.000