Source code for astropy.coordinates.earth

# Licensed under a 3-clause BSD style license - see LICENSE.rst

from warnings import warn
import collections
import socket
import json
import urllib.request
import urllib.error
import urllib.parse

import numpy as np
import erfa

from astropy import units as u
from astropy import constants as consts
from astropy.units.quantity import QuantityInfoBase
from astropy.utils import data
from astropy.utils.decorators import format_doc
from astropy.utils.exceptions import AstropyUserWarning

from .angles import Angle, Longitude, Latitude
from .representation import (BaseRepresentation, CartesianRepresentation,
                             CartesianDifferential)
from .matrix_utilities import matrix_transpose
from .errors import UnknownSiteException


__all__ = ['EarthLocation', 'BaseGeodeticRepresentation',
           'WGS84GeodeticRepresentation', 'WGS72GeodeticRepresentation',
           'GRS80GeodeticRepresentation']

GeodeticLocation = collections.namedtuple('GeodeticLocation', ['lon', 'lat', 'height'])

ELLIPSOIDS = {}
"""Available ellipsoids (defined in erfam.h, with numbers exposed in erfa)."""
# Note: they get filled by the creation of the geodetic classes.

OMEGA_EARTH = ((1.002_737_811_911_354_48 * u.cycle/u.day)
               .to(1/u.s, u.dimensionless_angles()))
"""
Rotational velocity of Earth, following SOFA's pvtob.

In UT1 seconds, this would be 2 pi / (24 * 3600), but we need the value
in SI seconds, so multiply by the ratio of stellar to solar day.
See Explanatory Supplement to the Astronomical Almanac, ed. P. Kenneth
Seidelmann (1992), University Science Books. The constant is the
conventional, exact one (IERS conventions 2003); see
http://hpiers.obspm.fr/eop-pc/index.php?index=constants.
"""


def _check_ellipsoid(ellipsoid=None, default='WGS84'):
    if ellipsoid is None:
        ellipsoid = default
    if ellipsoid not in ELLIPSOIDS:
        raise ValueError(f'Ellipsoid {ellipsoid} not among known ones ({ELLIPSOIDS})')
    return ellipsoid


def _get_json_result(url, err_str, use_google):

    # need to do this here to prevent a series of complicated circular imports
    from .name_resolve import NameResolveError
    try:
        # Retrieve JSON response from Google maps API
        resp = urllib.request.urlopen(url, timeout=data.conf.remote_timeout)
        resp_data = json.loads(resp.read().decode('utf8'))

    except urllib.error.URLError as e:
        # This catches a timeout error, see:
        #   http://stackoverflow.com/questions/2712524/handling-urllib2s-timeout-python
        if isinstance(e.reason, socket.timeout):
            raise NameResolveError(err_str.format(msg="connection timed out")) from e
        else:
            raise NameResolveError(err_str.format(msg=e.reason)) from e

    except socket.timeout:
        # There are some cases where urllib2 does not catch socket.timeout
        # especially while receiving response data on an already previously
        # working request
        raise NameResolveError(err_str.format(msg="connection timed out"))

    if use_google:
        results = resp_data.get('results', [])

        if resp_data.get('status', None) != 'OK':
            raise NameResolveError(err_str.format(msg="unknown failure with "
                                                  "Google API"))

    else:  # OpenStreetMap returns a list
        results = resp_data

    if not results:
        raise NameResolveError(err_str.format(msg="no results returned"))

    return results


class EarthLocationInfo(QuantityInfoBase):
    """
    Container for meta information like name, description, format.  This is
    required when the object is used as a mixin column within a table, but can
    be used as a general way to store meta information.
    """
    _represent_as_dict_attrs = ('x', 'y', 'z', 'ellipsoid')

    def _construct_from_dict(self, map):
        # Need to pop ellipsoid off and update post-instantiation.  This is
        # on the to-fix list in #4261.
        ellipsoid = map.pop('ellipsoid')
        out = self._parent_cls(**map)
        out.ellipsoid = ellipsoid
        return out

    def new_like(self, cols, length, metadata_conflicts='warn', name=None):
        """
        Return a new EarthLocation instance which is consistent with the
        input ``cols`` and has ``length`` rows.

        This is intended for creating an empty column object whose elements can
        be set in-place for table operations like join or vstack.

        Parameters
        ----------
        cols : list
            List of input columns
        length : int
            Length of the output column object
        metadata_conflicts : str ('warn'|'error'|'silent')
            How to handle metadata conflicts
        name : str
            Output column name

        Returns
        -------
        col : EarthLocation (or subclass)
            Empty instance of this class consistent with ``cols``
        """
        # Very similar to QuantityInfo.new_like, but the creation of the
        # map is different enough that this needs its own rouinte.
        # Get merged info attributes shape, dtype, format, description.
        attrs = self.merge_cols_attributes(cols, metadata_conflicts, name,
                                           ('meta', 'format', 'description'))
        # The above raises an error if the dtypes do not match, but returns
        # just the string representation, which is not useful, so remove.
        attrs.pop('dtype')
        # Make empty EarthLocation using the dtype and unit of the last column.
        # Use zeros so we do not get problems for possible conversion to
        # geodetic coordinates.
        shape = (length,) + attrs.pop('shape')
        data = u.Quantity(np.zeros(shape=shape, dtype=cols[0].dtype),
                          unit=cols[0].unit, copy=False)
        # Get arguments needed to reconstruct class
        map = {key: (data[key] if key in 'xyz' else getattr(cols[-1], key))
               for key in self._represent_as_dict_attrs}
        out = self._construct_from_dict(map)
        # Set remaining info attributes
        for attr, value in attrs.items():
            setattr(out.info, attr, value)

        return out


[docs]class EarthLocation(u.Quantity): """ Location on the Earth. Initialization is first attempted assuming geocentric (x, y, z) coordinates are given; if that fails, another attempt is made assuming geodetic coordinates (longitude, latitude, height above a reference ellipsoid). When using the geodetic forms, Longitudes are measured increasing to the east, so west longitudes are negative. Internally, the coordinates are stored as geocentric. To ensure a specific type of coordinates is used, use the corresponding class methods (`from_geocentric` and `from_geodetic`) or initialize the arguments with names (``x``, ``y``, ``z`` for geocentric; ``lon``, ``lat``, ``height`` for geodetic). See the class methods for details. Notes ----- This class fits into the coordinates transformation framework in that it encodes a position on the `~astropy.coordinates.ITRS` frame. To get a proper `~astropy.coordinates.ITRS` object from this object, use the ``itrs`` property. """ _ellipsoid = 'WGS84' _location_dtype = np.dtype({'names': ['x', 'y', 'z'], 'formats': [np.float64]*3}) _array_dtype = np.dtype((np.float64, (3,))) info = EarthLocationInfo() def __new__(cls, *args, **kwargs): # TODO: needs copy argument and better dealing with inputs. if (len(args) == 1 and len(kwargs) == 0 and isinstance(args[0], EarthLocation)): return args[0].copy() try: self = cls.from_geocentric(*args, **kwargs) except (u.UnitsError, TypeError) as exc_geocentric: try: self = cls.from_geodetic(*args, **kwargs) except Exception as exc_geodetic: raise TypeError('Coordinates could not be parsed as either ' 'geocentric or geodetic, with respective ' 'exceptions "{}" and "{}"' .format(exc_geocentric, exc_geodetic)) return self
[docs] @classmethod def from_geocentric(cls, x, y, z, unit=None): """ Location on Earth, initialized from geocentric coordinates. Parameters ---------- x, y, z : `~astropy.units.Quantity` or array-like Cartesian coordinates. If not quantities, ``unit`` should be given. unit : unit-like or None Physical unit of the coordinate values. If ``x``, ``y``, and/or ``z`` are quantities, they will be converted to this unit. Raises ------ astropy.units.UnitsError If the units on ``x``, ``y``, and ``z`` do not match or an invalid unit is given. ValueError If the shapes of ``x``, ``y``, and ``z`` do not match. TypeError If ``x`` is not a `~astropy.units.Quantity` and no unit is given. """ if unit is None: try: unit = x.unit except AttributeError: raise TypeError("Geocentric coordinates should be Quantities " "unless an explicit unit is given.") from None else: unit = u.Unit(unit) if unit.physical_type != 'length': raise u.UnitsError("Geocentric coordinates should be in " "units of length.") try: x = u.Quantity(x, unit, copy=False) y = u.Quantity(y, unit, copy=False) z = u.Quantity(z, unit, copy=False) except u.UnitsError: raise u.UnitsError("Geocentric coordinate units should all be " "consistent.") x, y, z = np.broadcast_arrays(x, y, z) struc = np.empty(x.shape, cls._location_dtype) struc['x'], struc['y'], struc['z'] = x, y, z return super().__new__(cls, struc, unit, copy=False)
[docs] @classmethod def from_geodetic(cls, lon, lat, height=0., ellipsoid=None): """ Location on Earth, initialized from geodetic coordinates. Parameters ---------- lon : `~astropy.coordinates.Longitude` or float Earth East longitude. Can be anything that initialises an `~astropy.coordinates.Angle` object (if float, in degrees). lat : `~astropy.coordinates.Latitude` or float Earth latitude. Can be anything that initialises an `~astropy.coordinates.Latitude` object (if float, in degrees). height : `~astropy.units.Quantity` ['length'] or float, optional Height above reference ellipsoid (if float, in meters; default: 0). ellipsoid : str, optional Name of the reference ellipsoid to use (default: 'WGS84'). Available ellipsoids are: 'WGS84', 'GRS80', 'WGS72'. Raises ------ astropy.units.UnitsError If the units on ``lon`` and ``lat`` are inconsistent with angular ones, or that on ``height`` with a length. ValueError If ``lon``, ``lat``, and ``height`` do not have the same shape, or if ``ellipsoid`` is not recognized as among the ones implemented. Notes ----- For the conversion to geocentric coordinates, the ERFA routine ``gd2gc`` is used. See https://github.com/liberfa/erfa """ ellipsoid = _check_ellipsoid(ellipsoid, default=cls._ellipsoid) # As wrapping fails on readonly input, we do so manually lon = Angle(lon, u.degree, copy=False).wrap_at(180 * u.degree) lat = Latitude(lat, u.degree, copy=False) # don't convert to m by default, so we can use the height unit below. if not isinstance(height, u.Quantity): height = u.Quantity(height, u.m, copy=False) # get geocentric coordinates. geodetic = ELLIPSOIDS[ellipsoid](lon, lat, height, copy=False) xyz = geodetic.to_cartesian().get_xyz(xyz_axis=-1) << height.unit self = xyz.view(cls._location_dtype, cls).reshape(geodetic.shape) self._ellipsoid = ellipsoid return self
[docs] @classmethod def of_site(cls, site_name): """ Return an object of this class for a known observatory/site by name. This is intended as a quick convenience function to get basic site information, not a fully-featured exhaustive registry of observatories and all their properties. Additional information about the site is stored in the ``.info.meta`` dictionary of sites obtained using this method (see the examples below). .. note:: When this function is called, it will attempt to download site information from the astropy data server. If you would like a site to be added, issue a pull request to the `astropy-data repository <https://github.com/astropy/astropy-data>`_ . If a site cannot be found in the registry (i.e., an internet connection is not available), it will fall back on a built-in list, In the future, this bundled list might include a version-controlled list of canonical observatories extracted from the online version, but it currently only contains the Greenwich Royal Observatory as an example case. Parameters ---------- site_name : str Name of the observatory (case-insensitive). Returns ------- site : `~astropy.coordinates.EarthLocation` (or subclass) instance The location of the observatory. The returned class will be the same as this class. Examples -------- >>> from astropy.coordinates import EarthLocation >>> keck = EarthLocation.of_site('Keck Observatory') # doctest: +REMOTE_DATA >>> keck.geodetic # doctest: +REMOTE_DATA +FLOAT_CMP GeodeticLocation(lon=<Longitude -155.47833333 deg>, lat=<Latitude 19.82833333 deg>, height=<Quantity 4160. m>) >>> keck.info # doctest: +REMOTE_DATA name = W. M. Keck Observatory dtype = void192 unit = m class = EarthLocation n_bad = 0 >>> keck.info.meta # doctest: +REMOTE_DATA {'source': 'IRAF Observatory Database', 'timezone': 'US/Hawaii'} See Also -------- get_site_names : the list of sites that this function can access """ # noqa registry = cls._get_site_registry() try: el = registry[site_name] except UnknownSiteException as e: raise UnknownSiteException(e.site, 'EarthLocation.get_site_names', close_names=e.close_names) from e if cls is el.__class__: return el else: newel = cls.from_geodetic(*el.to_geodetic()) newel.info.name = el.info.name return newel
[docs] @classmethod def of_address(cls, address, get_height=False, google_api_key=None): """ Return an object of this class for a given address by querying either the OpenStreetMap Nominatim tool [1]_ (default) or the Google geocoding API [2]_, which requires a specified API key. This is intended as a quick convenience function to get easy access to locations. If you need to specify a precise location, you should use the initializer directly and pass in a longitude, latitude, and elevation. In the background, this just issues a web query to either of the APIs noted above. This is not meant to be abused! Both OpenStreetMap and Google use IP-based query limiting and will ban your IP if you send more than a few thousand queries per hour [2]_. .. warning:: If the query returns more than one location (e.g., searching on ``address='springfield'``), this function will use the **first** returned location. Parameters ---------- address : str The address to get the location for. As per the Google maps API, this can be a fully specified street address (e.g., 123 Main St., New York, NY) or a city name (e.g., Danbury, CT), or etc. get_height : bool, optional This only works when using the Google API! See the ``google_api_key`` block below. Use the retrieved location to perform a second query to the Google maps elevation API to retrieve the height of the input address [3]_. google_api_key : str, optional A Google API key with the Geocoding API and (optionally) the elevation API enabled. See [4]_ for more information. Returns ------- location : `~astropy.coordinates.EarthLocation` (or subclass) instance The location of the input address. Will be type(this class) References ---------- .. [1] https://nominatim.openstreetmap.org/ .. [2] https://developers.google.com/maps/documentation/geocoding/start .. [3] https://developers.google.com/maps/documentation/elevation/start .. [4] https://developers.google.com/maps/documentation/geocoding/get-api-key """ use_google = google_api_key is not None # Fail fast if invalid options are passed: if not use_google and get_height: raise ValueError( 'Currently, `get_height` only works when using ' 'the Google geocoding API, which requires passing ' 'a Google API key with `google_api_key`. See: ' 'https://developers.google.com/maps/documentation/geocoding/get-api-key ' 'for information on obtaining an API key.') if use_google: # Google pars = urllib.parse.urlencode({'address': address, 'key': google_api_key}) geo_url = f"https://maps.googleapis.com/maps/api/geocode/json?{pars}" else: # OpenStreetMap pars = urllib.parse.urlencode({'q': address, 'format': 'json'}) geo_url = f"https://nominatim.openstreetmap.org/search?{pars}" # get longitude and latitude location err_str = f"Unable to retrieve coordinates for address '{address}'; {{msg}}" geo_result = _get_json_result(geo_url, err_str=err_str, use_google=use_google) if use_google: loc = geo_result[0]['geometry']['location'] lat = loc['lat'] lon = loc['lng'] else: loc = geo_result[0] lat = float(loc['lat']) # strings are returned by OpenStreetMap lon = float(loc['lon']) if get_height: pars = {'locations': f'{lat:.8f},{lon:.8f}', 'key': google_api_key} pars = urllib.parse.urlencode(pars) ele_url = f"https://maps.googleapis.com/maps/api/elevation/json?{pars}" err_str = f"Unable to retrieve elevation for address '{address}'; {{msg}}" ele_result = _get_json_result(ele_url, err_str=err_str, use_google=use_google) height = ele_result[0]['elevation']*u.meter else: height = 0. return cls.from_geodetic(lon=lon*u.deg, lat=lat*u.deg, height=height)
[docs] @classmethod def get_site_names(cls): """ Get list of names of observatories for use with `~astropy.coordinates.EarthLocation.of_site`. .. note:: When this function is called, it will first attempt to download site information from the astropy data server. If it cannot (i.e., an internet connection is not available), it will fall back on the list included with astropy (which is a limited and dated set of sites). If you think a site should be added, issue a pull request to the `astropy-data repository <https://github.com/astropy/astropy-data>`_ . Returns ------- names : list of str List of valid observatory names See Also -------- of_site : Gets the actual location object for one of the sites names this returns. """ return cls._get_site_registry().names
@classmethod def _get_site_registry(cls, force_download=False, force_builtin=False): """ Gets the site registry. The first time this either downloads or loads from the data file packaged with astropy. Subsequent calls will use the cached version unless explicitly overridden. Parameters ---------- force_download : bool or str If not False, force replacement of the cached registry with a downloaded version. If a str, that will be used as the URL to download from (if just True, the default URL will be used). force_builtin : bool If True, load from the data file bundled with astropy and set the cache to that. Returns ------- reg : astropy.coordinates.sites.SiteRegistry """ # need to do this here at the bottom to avoid circular dependencies from .sites import get_builtin_sites, get_downloaded_sites if force_builtin and force_download: raise ValueError('Cannot have both force_builtin and force_download True') if force_builtin: reg = cls._site_registry = get_builtin_sites() else: reg = getattr(cls, '_site_registry', None) if force_download or not reg: try: if isinstance(force_download, str): reg = get_downloaded_sites(force_download) else: reg = get_downloaded_sites() except OSError: if force_download: raise msg = ('Could not access the online site list. Falling ' 'back on the built-in version, which is rather ' 'limited. If you want to retry the download, do ' '{0}._get_site_registry(force_download=True)') warn(AstropyUserWarning(msg.format(cls.__name__))) reg = get_builtin_sites() cls._site_registry = reg return reg @property def ellipsoid(self): """The default ellipsoid used to convert to geodetic coordinates.""" return self._ellipsoid @ellipsoid.setter def ellipsoid(self, ellipsoid): self._ellipsoid = _check_ellipsoid(ellipsoid) @property def geodetic(self): """Convert to geodetic coordinates for the default ellipsoid.""" return self.to_geodetic()
[docs] def to_geodetic(self, ellipsoid=None): """Convert to geodetic coordinates. Parameters ---------- ellipsoid : str, optional Reference ellipsoid to use. Default is the one the coordinates were initialized with. Available are: 'WGS84', 'GRS80', 'WGS72' Returns ------- lon, lat, height : `~astropy.units.Quantity` The tuple is a ``GeodeticLocation`` namedtuple and is comprised of instances of `~astropy.coordinates.Longitude`, `~astropy.coordinates.Latitude`, and `~astropy.units.Quantity`. Raises ------ ValueError if ``ellipsoid`` is not recognized as among the ones implemented. Notes ----- For the conversion to geodetic coordinates, the ERFA routine ``gc2gd`` is used. See https://github.com/liberfa/erfa """ ellipsoid = _check_ellipsoid(ellipsoid, default=self.ellipsoid) xyz = self.view(self._array_dtype, u.Quantity) llh = CartesianRepresentation(xyz, xyz_axis=-1, copy=False).represent_as( ELLIPSOIDS[ellipsoid]) return GeodeticLocation( Longitude(llh.lon, u.deg, wrap_angle=180*u.deg, copy=False), llh.lat << u.deg, llh.height << self.unit)
@property def lon(self): """Longitude of the location, for the default ellipsoid.""" return self.geodetic[0] @property def lat(self): """Latitude of the location, for the default ellipsoid.""" return self.geodetic[1] @property def height(self): """Height of the location, for the default ellipsoid.""" return self.geodetic[2] # mostly for symmetry with geodetic and to_geodetic. @property def geocentric(self): """Convert to a tuple with X, Y, and Z as quantities""" return self.to_geocentric()
[docs] def to_geocentric(self): """Convert to a tuple with X, Y, and Z as quantities""" return (self.x, self.y, self.z)
[docs] def get_itrs(self, obstime=None): """ Generates an `~astropy.coordinates.ITRS` object with the location of this object at the requested ``obstime``. Parameters ---------- obstime : `~astropy.time.Time` or None The ``obstime`` to apply to the new `~astropy.coordinates.ITRS`, or if None, the default ``obstime`` will be used. Returns ------- itrs : `~astropy.coordinates.ITRS` The new object in the ITRS frame """ # Broadcast for a single position at multiple times, but don't attempt # to be more general here. if obstime and self.size == 1 and obstime.shape: self = np.broadcast_to(self, obstime.shape, subok=True) # do this here to prevent a series of complicated circular imports from .builtin_frames import ITRS return ITRS(x=self.x, y=self.y, z=self.z, obstime=obstime)
itrs = property(get_itrs, doc="""An `~astropy.coordinates.ITRS` object with for the location of this object at the default ``obstime``.""")
[docs] def get_gcrs(self, obstime): """GCRS position with velocity at ``obstime`` as a GCRS coordinate. Parameters ---------- obstime : `~astropy.time.Time` The ``obstime`` to calculate the GCRS position/velocity at. Returns ------- gcrs : `~astropy.coordinates.GCRS` instance With velocity included. """ # do this here to prevent a series of complicated circular imports from .builtin_frames import GCRS loc, vel = self.get_gcrs_posvel(obstime) loc.differentials['s'] = CartesianDifferential.from_cartesian(vel) return GCRS(loc, obstime=obstime)
def _get_gcrs_posvel(self, obstime, ref_to_itrs, gcrs_to_ref): """Calculate GCRS position and velocity given transformation matrices. The reference frame z axis must point to the Celestial Intermediate Pole (as is the case for CIRS and TETE). This private method is used in intermediate_rotation_transforms, where some of the matrices are already available for the coordinate transformation. The method is faster by an order of magnitude than just adding a zero velocity to ITRS and transforming to GCRS, because it avoids calculating the velocity via finite differencing of the results of the transformation at three separate times. """ # The simplest route is to transform to the reference frame where the # z axis is properly aligned with the Earth's rotation axis (CIRS or # TETE), then calculate the velocity, and then transform this # reference position and velocity to GCRS. For speed, though, we # transform the coordinates to GCRS in one step, and calculate the # velocities by rotating around the earth's axis transformed to GCRS. ref_to_gcrs = matrix_transpose(gcrs_to_ref) itrs_to_gcrs = ref_to_gcrs @ matrix_transpose(ref_to_itrs) # Earth's rotation vector in the ref frame is rot_vec_ref = (0,0,OMEGA_EARTH), # so in GCRS it is rot_vec_gcrs[..., 2] @ OMEGA_EARTH. rot_vec_gcrs = CartesianRepresentation(ref_to_gcrs[..., 2] * OMEGA_EARTH, xyz_axis=-1, copy=False) # Get the position in the GCRS frame. # Since we just need the cartesian representation of ITRS, avoid get_itrs(). itrs_cart = CartesianRepresentation(self.x, self.y, self.z, copy=False) pos = itrs_cart.transform(itrs_to_gcrs) vel = rot_vec_gcrs.cross(pos) return pos, vel
[docs] def get_gcrs_posvel(self, obstime): """ Calculate the GCRS position and velocity of this object at the requested ``obstime``. Parameters ---------- obstime : `~astropy.time.Time` The ``obstime`` to calculate the GCRS position/velocity at. Returns ------- obsgeoloc : `~astropy.coordinates.CartesianRepresentation` The GCRS position of the object obsgeovel : `~astropy.coordinates.CartesianRepresentation` The GCRS velocity of the object """ # Local import to prevent circular imports. from .builtin_frames.intermediate_rotation_transforms import ( cirs_to_itrs_mat, gcrs_to_cirs_mat) # Get gcrs_posvel by transforming via CIRS (slightly faster than TETE). return self._get_gcrs_posvel(obstime, cirs_to_itrs_mat(obstime), gcrs_to_cirs_mat(obstime))
[docs] def gravitational_redshift(self, obstime, bodies=['sun', 'jupiter', 'moon'], masses={}): """Return the gravitational redshift at this EarthLocation. Calculates the gravitational redshift, of order 3 m/s, due to the requested solar system bodies. Parameters ---------- obstime : `~astropy.time.Time` The ``obstime`` to calculate the redshift at. bodies : iterable, optional The bodies (other than the Earth) to include in the redshift calculation. List elements should be any body name `get_body_barycentric` accepts. Defaults to Jupiter, the Sun, and the Moon. Earth is always included (because the class represents an *Earth* location). masses : dict[str, `~astropy.units.Quantity`], optional The mass or gravitational parameters (G * mass) to assume for the bodies requested in ``bodies``. Can be used to override the defaults for the Sun, Jupiter, the Moon, and the Earth, or to pass in masses for other bodies. Returns ------- redshift : `~astropy.units.Quantity` Gravitational redshift in velocity units at given obstime. """ # needs to be here to avoid circular imports from .solar_system import get_body_barycentric bodies = list(bodies) # Ensure earth is included and last in the list. if 'earth' in bodies: bodies.remove('earth') bodies.append('earth') _masses = {'sun': consts.GM_sun, 'jupiter': consts.GM_jup, 'moon': consts.G * 7.34767309e22*u.kg, 'earth': consts.GM_earth} _masses.update(masses) GMs = [] M_GM_equivalency = (u.kg, u.Unit(consts.G * u.kg)) for body in bodies: try: GMs.append(_masses[body].to(u.m**3/u.s**2, [M_GM_equivalency])) except KeyError as err: raise KeyError(f'body "{body}" does not have a mass.') from err except u.UnitsError as exc: exc.args += ('"masses" argument values must be masses or ' 'gravitational parameters.',) raise positions = [get_body_barycentric(name, obstime) for name in bodies] # Calculate distances to objects other than earth. distances = [(pos - positions[-1]).norm() for pos in positions[:-1]] # Append distance from Earth's center for Earth's contribution. distances.append(CartesianRepresentation(self.geocentric).norm()) # Get redshifts due to all objects. redshifts = [-GM / consts.c / distance for (GM, distance) in zip(GMs, distances)] # Reverse order of summing, to go from small to big, and to get # "earth" first, which gives m/s as unit. return sum(redshifts[::-1])
@property def x(self): """The X component of the geocentric coordinates.""" return self['x'] @property def y(self): """The Y component of the geocentric coordinates.""" return self['y'] @property def z(self): """The Z component of the geocentric coordinates.""" return self['z'] def __getitem__(self, item): result = super().__getitem__(item) if result.dtype is self.dtype: return result.view(self.__class__) else: return result.view(u.Quantity) def __array_finalize__(self, obj): super().__array_finalize__(obj) if hasattr(obj, '_ellipsoid'): self._ellipsoid = obj._ellipsoid def __len__(self): if self.shape == (): raise IndexError('0-d EarthLocation arrays cannot be indexed') else: return super().__len__() def _to_value(self, unit, equivalencies=[]): """Helper method for to and to_value.""" # Conversion to another unit in both ``to`` and ``to_value`` goes # via this routine. To make the regular quantity routines work, we # temporarily turn the structured array into a regular one. array_view = self.view(self._array_dtype, np.ndarray) if equivalencies == []: equivalencies = self._equivalencies new_array = self.unit.to(unit, array_view, equivalencies=equivalencies) return new_array.view(self.dtype).reshape(self.shape)
geodetic_base_doc = """{__doc__} Parameters ---------- lon, lat : angle-like 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 `~astropy.coordinates.Angle` and either `~astropy.coordinates.Longitude` not `~astropy.coordinates.Latitude`, depending on the parameter. height : `~astropy.units.Quantity` ['length'] The height to the point(s). copy : bool, optional If `True` (default), arrays will be copied. If `False`, arrays will be references, though possibly broadcast to ensure matching shapes. """
[docs]@format_doc(geodetic_base_doc) class BaseGeodeticRepresentation(BaseRepresentation): """Base geodetic representation.""" attr_classes = {'lon': Longitude, 'lat': Latitude, 'height': u.Quantity} def __init_subclass__(cls, **kwargs): super().__init_subclass__(**kwargs) if '_ellipsoid' in cls.__dict__: ELLIPSOIDS[cls._ellipsoid] = cls def __init__(self, lon, lat=None, height=None, copy=True): if height is None and not isinstance(lon, self.__class__): height = 0 << u.m super().__init__(lon, lat, height, copy=copy) if not self.height.unit.is_equivalent(u.m): raise u.UnitTypeError(f"{self.__class__.__name__} requires " f"height with units of length.")
[docs] def to_cartesian(self): """ Converts WGS84 geodetic coordinates to 3D rectangular (geocentric) cartesian coordinates. """ xyz = erfa.gd2gc(getattr(erfa, self._ellipsoid), self.lon, self.lat, self.height) return CartesianRepresentation(xyz, xyz_axis=-1, copy=False)
[docs] @classmethod def from_cartesian(cls, cart): """ Converts 3D rectangular cartesian coordinates (assumed geocentric) to WGS84 geodetic coordinates. """ lon, lat, height = erfa.gc2gd(getattr(erfa, cls._ellipsoid), cart.get_xyz(xyz_axis=-1)) return cls(lon, lat, height, copy=False)
@format_doc(geodetic_base_doc) class WGS84GeodeticRepresentation(BaseGeodeticRepresentation): """Representation of points in WGS84 3D geodetic coordinates.""" _ellipsoid = 'WGS84' @format_doc(geodetic_base_doc) class WGS72GeodeticRepresentation(BaseGeodeticRepresentation): """Representation of points in WGS72 3D geodetic coordinates.""" _ellipsoid = 'WGS72'
[docs]@format_doc(geodetic_base_doc) class GRS80GeodeticRepresentation(BaseGeodeticRepresentation): """Representation of points in GRS80 3D geodetic coordinates.""" _ellipsoid = 'GRS80'