EarthLocation

class astropy.coordinates.EarthLocation

Bases: astropy.units.quantity.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 ITRS frame. To get a proper ITRS object from this object, use the itrs property.

Attributes Summary

ellipsoid	The default ellipsoid used to convert to geodetic coordinates.
geocentric	Convert to a tuple with X, Y, and Z as quantities
geodetic	Convert to geodetic coordinates for the default ellipsoid.
height	Height of the location, for the default ellipsoid.
itrs	An ITRS object with for the location of this object at the default obstime.
latitude	Latitude of the location, for the default ellipsoid.
longitude	Longitude of the location, for the default ellipsoid.
x	The X component of the geocentric coordinates.
y	The Y component of the geocentric coordinates.
z	The Z component of the geocentric coordinates.

Methods Summary

from_geocentric(x, y, z[, unit])	Location on Earth, initialized from geocentric coordinates.
from_geodetic(lon, lat[, height, ellipsoid])	Location on Earth, initialized from geodetic coordinates.
get_itrs([obstime])	Generates an ITRS object with the location of this object at the requested obstime.
get_site_names()	Get list of names of observatories for use with of_site.
of_site(site_name)	Return an object of this class for a known observatory/site by name.
to(unit[, equivalencies])	Returns a new Quantity object with the specified units.
to_geocentric()	Convert to a tuple with X, Y, and Z as quantities
to_geodetic([ellipsoid])	Convert to geodetic coordinates.

Attributes Documentation

ellipsoid

The default ellipsoid used to convert to geodetic coordinates.

geocentric

Convert to a tuple with X, Y, and Z as quantities

geodetic

Convert to geodetic coordinates for the default ellipsoid.

height

Height of the location, for the default ellipsoid.

itrs

An ITRS object with for the location of this object at the default obstime.

latitude

Latitude of the location, for the default ellipsoid.

longitude

Longitude of the location, for the default ellipsoid.

x

The X component of the geocentric coordinates.

y

The Y component of the geocentric coordinates.

z

The Z component of the geocentric coordinates.

Methods Documentation

classmethod from_geocentric(x, y, z, unit=None)

Location on Earth, initialized from geocentric coordinates.

Parameters:

x, y, z : Quantity or array-like

Cartesian coordinates. If not quantities, unit should be given.

unit : UnitBase object 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 Quantity and no unit is given.

classmethod from_geodetic(lon, lat, height=0.0, ellipsoid=None)

Location on Earth, initialized from geodetic coordinates.

Parameters:

lon : Longitude or float

Earth East longitude. Can be anything that initialises an Angle object (if float, in degrees).

lat : Latitude or float

Earth latitude. Can be anything that initialises an Latitude object (if float, in degrees).

height : Quantity 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

get_itrs(obstime=None)

Generates an ITRS object with the location of this object at the requested obstime.

Parameters:

obstime : Time or None

The obstime to apply to the new ITRS, or if None, the default obstime will be used.

Returns:

itrs : ITRS

The new object in the ITRS frame

classmethod get_site_names()

Get list of names of observatories for use with 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 .

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.

classmethod of_site(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.

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 . 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 : This class (a EarthLocation or subclass)

The location of the observatory.

See also

get_site_names

the list of sites that this function can access

to(unit, equivalencies=[])

Returns a new Quantity object with the specified units.

Parameters:

unit : UnitBase instance, str

An object that represents the unit to convert to. Must be an UnitBase object or a string parseable by the units package.

equivalencies : list of equivalence pairs, optional

A list of equivalence pairs to try if the units are not directly convertible. See Equivalencies. If not provided or [], class default equivalencies will be used (none for Quantity, but may be set for subclasses) If None, no equivalencies will be applied at all, not even any set globally or within a context.

to_geocentric()

Convert to a tuple with X, Y, and Z as quantities

to_geodetic(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) : tuple

The tuple contains instances of Longitude, Latitude, and 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