astropy:docs

Note

This is an old version of the documentation. See http://docs.astropy.org/en/stable for the latest version.

EarthLocation

class astropy.coordinates.EarthLocation[source] [edit on github]

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 Generates an ITRS object with the coordinates of this object.
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.
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

Generates an ITRS object with the coordinates of this object.

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)[source] [edit on github]

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)[source] [edit on github]

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

to(unit, equivalencies=[])[source] [edit on github]

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()[source] [edit on github]

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

to_geodetic(ellipsoid=None)[source] [edit on github]

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

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