# iris.coord_systems#

Definitions of coordinate systems.

In this module:

A coordinate system in the Albers Conical Equal Area projection.

classiris.coord_systems.AlbersEqualArea(latitude_of_projection_origin=None,longitude_of_central_meridian=None,false_easting=None,false_northing=None,standard_parallels=None,ellipsoid=None)[source]#Constructs a Albers Conical Equal Area coord system.

Kwargs:

- latitude_of_projection_origin:
True latitude of planar origin in degrees. Defaults to 0.0 .

- longitude_of_central_meridian:
True longitude of planar central meridian in degrees. Defaults to 0.0 .

- false_easting:
X offset from planar origin in metres. Defaults to 0.0 .

- false_northing:
Y offset from planar origin in metres. Defaults to 0.0 .

- standard_parallels (number or iterable of 1 or 2 numbers):
The one or two latitudes of correct scale. Defaults to (20.0, 50.0).

- ellipsoid (
`GeogCS`

):If given, defines the ellipsoid.

- __eq__(
other)#Override equality

The _globe and _crs attributes are not compared because they are cached properties and completely derived from other attributes. The nature of caching means that they can appear on one object and not on another despite the objects being identical, and them being completely derived from other attributes means they will only differ if other attributes that are being tested for equality differ.

- as_cartopy_projection()[source]#
Return a cartopy projection representing our native map.

This will be the same as the

`as_cartopy_crs()`

for map projections but for spherical coord systems (which are not map projections) we use a map projection, such as PlateCarree.

- xml_element(
doc,attrs=None)#Default behaviour for coord systems.

- false_easting#
X offset from planar origin in metres.

- false_northing#
Y offset from planar origin in metres.

- grid_mapping_name
= 'albers_conical_equal_area'#

- latitude_of_projection_origin#
True latitude of planar origin in degrees.

- longitude_of_central_meridian#
True longitude of planar central meridian in degrees.

- standard_parallels#
The one or two latitudes of correct scale (tuple of 1 or 2 floats).

Abstract base class for coordinate systems.

classiris.coord_systems.CoordSystem[source]#Abstract base class for coordinate systems.

- __eq__(
other)[source]#Override equality

The _globe and _crs attributes are not compared because they are cached properties and completely derived from other attributes. The nature of caching means that they can appear on one object and not on another despite the objects being identical, and them being completely derived from other attributes means they will only differ if other attributes that are being tested for equality differ.

abstractas_cartopy_projection()[source]#Return a cartopy projection representing our native map.

This will be the same as the

`as_cartopy_crs()`

for map projections but for spherical coord systems (which are not map projections) we use a map projection, such as PlateCarree.

- grid_mapping_name
= None#

A geographic (ellipsoidal) coordinate system, defined by the shape of the Earth and a prime meridian.

classiris.coord_systems.GeogCS(semi_major_axis=None,semi_minor_axis=None,inverse_flattening=None,longitude_of_prime_meridian=None)[source]#Create a new GeogCS.

- Parameters

semi_major_axis(*) – Axes of ellipsoid, in metres. At least one must be given (see note below).

semi_minor_axis– Axes of ellipsoid, in metres. At least one must be given (see note below).

inverse_flattening(*) – Can be omitted if both axes given (see note below). Default 0.0

longitude_of_prime_meridian(*) – Specifies the prime meridian on the ellipsoid, in degrees. Default 0.0Notes

If just semi_major_axis is set, with no semi_minor_axis or inverse_flattening, then a perfect sphere is created from the given radius.

If just two of semi_major_axis, semi_minor_axis, and inverse_flattening are given the missing element is calculated from the formula: \(flattening = (major - minor) / major\)

Currently, Iris will not allow over-specification (all three ellipsoid parameters).

After object creation, altering any of these properties will not update the others. semi_major_axis and semi_minor_axis are used when creating Cartopy objects.

Examples:

cs = GeogCS(6371229) pp_cs = GeogCS(iris.fileformats.pp.EARTH_RADIUS) airy1830 = GeogCS(semi_major_axis=6377563.396, semi_minor_axis=6356256.909) airy1830 = GeogCS(semi_major_axis=6377563.396, inverse_flattening=299.3249646) custom_cs = GeogCS(6400000, 6300000)

- __eq__(
other)#Override equality

The _globe and _crs attributes are not compared because they are cached properties and completely derived from other attributes. The nature of caching means that they can appear on one object and not on another despite the objects being identical, and them being completely derived from other attributes means they will only differ if other attributes that are being tested for equality differ.

- as_cartopy_projection()[source]#
Return a cartopy projection representing our native map.

This will be the same as the

`as_cartopy_crs()`

for map projections but for spherical coord systems (which are not map projections) we use a map projection, such as PlateCarree.

propertydatum#

- grid_mapping_name
= 'latitude_longitude'#

propertyinverse_flattening#

- longitude_of_prime_meridian#
Describes ‘zero’ on the ellipsoid in degrees.

propertysemi_major_axis#

propertysemi_minor_axis#

A geostationary satellite image map projection.

classiris.coord_systems.Geostationary(latitude_of_projection_origin,longitude_of_projection_origin,perspective_point_height,sweep_angle_axis,false_easting=None,false_northing=None,ellipsoid=None)[source]#Constructs a Geostationary coord system.

Args:

- latitude_of_projection_origin:
True latitude of planar origin in degrees.

- longitude_of_projection_origin:
True longitude of planar origin in degrees.

- perspective_point_height:
Altitude of satellite in metres above the surface of the ellipsoid.

- sweep_angle_axis (string):
The axis along which the satellite instrument sweeps - ‘x’ or ‘y’.

Kwargs:

- false_easting:
X offset from planar origin in metres. Defaults to 0.0 .

- false_northing:
Y offset from planar origin in metres. Defaults to 0.0 .

- ellipsoid (
`GeogCS`

):If given, defines the ellipsoid.

- __eq__(
other)#Override equality

- as_cartopy_projection()[source]#
Return a cartopy projection representing our native map.

`as_cartopy_crs()`

for map projections but for spherical coord systems (which are not map projections) we use a map projection, such as PlateCarree.

- xml_element(
doc,attrs=None)#Default behaviour for coord systems.

- false_easting#
X offset from planar origin in metres.

- false_northing#
Y offset from planar origin in metres.

- grid_mapping_name
= 'geostationary'#

- latitude_of_projection_origin#
True latitude of planar origin in degrees.

- longitude_of_projection_origin#
True longitude of planar origin in degrees.

- perspective_point_height#
Altitude of satellite in metres.

- sweep_angle_axis#
The sweep angle axis (string ‘x’ or ‘y’).

A coordinate system in the Lambert Azimuthal Equal Area projection.

classiris.coord_systems.LambertAzimuthalEqualArea(latitude_of_projection_origin=None,longitude_of_projection_origin=None,false_easting=None,false_northing=None,ellipsoid=None)[source]#Constructs a Lambert Azimuthal Equal Area coord system.

Kwargs:

- latitude_of_projection_origin:
True latitude of planar origin in degrees. Defaults to 0.0 .

- longitude_of_projection_origin:
True longitude of planar origin in degrees. Defaults to 0.0 .

- false_easting:
X offset from planar origin in metres. Defaults to 0.0 .

- false_northing:
Y offset from planar origin in metres. Defaults to 0.0 .

- ellipsoid (
`GeogCS`

):If given, defines the ellipsoid.

- __eq__(
other)#Override equality

- as_cartopy_projection()[source]#
Return a cartopy projection representing our native map.

`as_cartopy_crs()`

for map projections but for spherical coord systems (which are not map projections) we use a map projection, such as PlateCarree.

- xml_element(
doc,attrs=None)#Default behaviour for coord systems.

- false_easting#
X offset from planar origin in metres.

- false_northing#
Y offset from planar origin in metres.

- grid_mapping_name
= 'lambert_azimuthal_equal_area'#

- latitude_of_projection_origin#
True latitude of planar origin in degrees.

- longitude_of_projection_origin#
True longitude of planar origin in degrees.

A coordinate system in the Lambert Conformal conic projection.

classiris.coord_systems.LambertConformal(central_lat=None,central_lon=None,false_easting=None,false_northing=None,secant_latitudes=None,ellipsoid=None)[source]#Constructs a LambertConformal coord system.

Kwargs:

- central_lat:
The latitude of “unitary scale”. Defaults to 39.0 .

- central_lon:
The central longitude. Defaults to -96.0 .

- false_easting:
X offset from planar origin in metres. Defaults to 0.0 .

- false_northing:
Y offset from planar origin in metres. Defaults to 0.0 .

- secant_latitudes (number or iterable of 1 or 2 numbers):
Latitudes of secant intersection. One or two. Defaults to (33.0, 45.0).

- ellipsoid (
`GeogCS`

):If given, defines the ellipsoid.

- __eq__(
other)#Override equality

- as_cartopy_projection()[source]#
Return a cartopy projection representing our native map.

`as_cartopy_crs()`

for map projections but for spherical coord systems (which are not map projections) we use a map projection, such as PlateCarree.

- xml_element(
doc,attrs=None)#Default behaviour for coord systems.

- central_lat#
True latitude of planar origin in degrees.

- central_lon#
True longitude of planar origin in degrees.

- false_easting#
X offset from planar origin in metres.

- false_northing#
Y offset from planar origin in metres.

- grid_mapping_name
= 'lambert_conformal_conic'#

- secant_latitudes#
The standard parallels of the cone (tuple of 1 or 2 floats).

A coordinate system in the Mercator projection.

classiris.coord_systems.Mercator(longitude_of_projection_origin=None,ellipsoid=None,standard_parallel=None,scale_factor_at_projection_origin=None,false_easting=None,false_northing=None)[source]#Constructs a Mercator coord system.

Kwargs:

- longitude_of_projection_origin:
True longitude of planar origin in degrees. Defaults to 0.0 .

- ellipsoid (
`GeogCS`

):If given, defines the ellipsoid.

- standard_parallel:
The latitude where the scale is 1. Defaults to 0.0 .

- scale_factor_at_projection_origin:
Scale factor at natural origin. Defaults to unused.

- false_easting:
X offset from the planar origin in metres. Defaults to 0.0.

- false_northing:
Y offset from the planar origin in metres. Defaults to 0.0.

- datum:
If given, specifies the datumof the coordinate system. Only respected if iris.Future.daum_support is set.

Note: Only one of

`standard_parallel`

and`scale_factor_at_projection_origin`

should be included.

- __eq__(
other)#Override equality

- as_cartopy_projection()[source]#
Return a cartopy projection representing our native map.

`as_cartopy_crs()`

for map projections but for spherical coord systems (which are not map projections) we use a map projection, such as PlateCarree.

- xml_element(
doc,attrs=None)#Default behaviour for coord systems.

- false_easting#
X offset from the planar origin in metres.

- false_northing#
Y offset from the planar origin in metres.

- grid_mapping_name
= 'mercator'#

- longitude_of_projection_origin#
True longitude of planar origin in degrees.

- standard_parallel#
The latitude where the scale is 1.

A Specific transverse mercator projection on a specific ellipsoid.

classiris.coord_systems.OSGB[source]#A Specific transverse mercator projection on a specific ellipsoid.

- __eq__(
other)#Override equality

- as_cartopy_projection()[source]#
Return a cartopy projection representing our native map.

`as_cartopy_crs()`

for map projections but for spherical coord systems (which are not map projections) we use a map projection, such as PlateCarree.

- xml_element(
doc,attrs=None)#Default behaviour for coord systems.

- false_easting#
X offset from planar origin in metres.

- false_northing#
Y offset from planar origin in metres.

- grid_mapping_name
= 'transverse_mercator'#

- latitude_of_projection_origin#
True latitude of planar origin in degrees.

- longitude_of_central_meridian#
True longitude of planar origin in degrees.

- scale_factor_at_central_meridian#
Scale factor at the centre longitude.

An orthographic map projection.

classiris.coord_systems.Orthographic(latitude_of_projection_origin,longitude_of_projection_origin,false_easting=None,false_northing=None,ellipsoid=None)[source]#Constructs an Orthographic coord system.

Args:

- latitude_of_projection_origin:
True latitude of planar origin in degrees.

- longitude_of_projection_origin:
True longitude of planar origin in degrees.

Kwargs:

- false_easting:
X offset from planar origin in metres. Defaults to 0.0 .

- false_northing:
Y offset from planar origin in metres. Defaults to 0.0 .

- ellipsoid (
`GeogCS`

):If given, defines the ellipsoid.

- __eq__(
other)#Override equality

- as_cartopy_projection()[source]#
Return a cartopy projection representing our native map.

`as_cartopy_crs()`

for map projections but for spherical coord systems (which are not map projections) we use a map projection, such as PlateCarree.

- xml_element(
doc,attrs=None)#Default behaviour for coord systems.

- false_easting#
X offset from planar origin in metres.

- false_northing#
Y offset from planar origin in metres.

- grid_mapping_name
= 'orthographic'#

- latitude_of_projection_origin#
True latitude of planar origin in degrees.

- longitude_of_projection_origin#
True longitude of planar origin in degrees.

A subclass of the stereographic map projection centred on a pole.

classiris.coord_systems.PolarStereographic(central_lat,central_lon,false_easting=None,false_northing=None,true_scale_lat=None,scale_factor_at_projection_origin=None,ellipsoid=None)[source]#Construct a Polar Stereographic coord system.

- Parameters

central_lat({90,-90}) – The latitude of the pole.

central_lon(float) – The central longitude, which aligns with the y axis.

false_easting(float,optional) – X offset from planar origin in metres.

false_northing(float,optional) – Y offset from planar origin in metres.

true_scale_lat(float,optional) – Latitude of true scale.

scale_factor_at_projection_origin(float,optional) – Scale factor at the origin of the projection

ellipsoid(`GeogCS`

, optional) – If given, defines the ellipsoid.Notes

It is only valid to provide at most one of true_scale_lat and scale_factor_at_projection_origin.

- __eq__(
other)#Override equality

- as_cartopy_crs()#
Return a cartopy CRS representing our native coordinate system.

- as_cartopy_projection()#
Return a cartopy projection representing our native map.

`as_cartopy_crs()`

for map projections but for spherical coord systems (which are not map projections) we use a map projection, such as PlateCarree.

- xml_element(
doc,attrs=None)#Default behaviour for coord systems.

- central_lat#
True latitude of planar origin in degrees.

- central_lon#
True longitude of planar origin in degrees.

- false_easting#
X offset from planar origin in metres.

- false_northing#
Y offset from planar origin in metres.

- grid_mapping_name
= 'polar_stereographic'#

- scale_factor_at_projection_origin#
Scale factor at projection origin.

- true_scale_lat#
Latitude of true scale.

A coordinate system with rotated pole, on an optional `GeogCS`

.

classiris.coord_systems.RotatedGeogCS(grid_north_pole_latitude,grid_north_pole_longitude,north_pole_grid_longitude=None,ellipsoid=None)[source]#Constructs a coordinate system with rotated pole, on an optional

`GeogCS`

.Args:

- grid_north_pole_latitude:
The true latitude of the rotated pole in degrees.

- grid_north_pole_longitude:
The true longitude of the rotated pole in degrees.

Kwargs:

- north_pole_grid_longitude:
Longitude of true north pole in rotated grid, in degrees. Defaults to 0.0 .

- ellipsoid (
`GeogCS`

):If given, defines the ellipsoid.

Examples:

rotated_cs = RotatedGeogCS(30, 30) another_cs = RotatedGeogCS(30, 30, ellipsoid=GeogCS(6400000, 6300000))

- __eq__(
other)#Override equality

- as_cartopy_projection()[source]#
Return a cartopy projection representing our native map.

`as_cartopy_crs()`

for map projections but for spherical coord systems (which are not map projections) we use a map projection, such as PlateCarree.

- grid_mapping_name
= 'rotated_latitude_longitude'#

- grid_north_pole_latitude#
The true latitude of the rotated pole in degrees.

- grid_north_pole_longitude#
The true longitude of the rotated pole in degrees.

- north_pole_grid_longitude#
Longitude of true north pole in rotated grid in degrees.

A stereographic map projection.

classiris.coord_systems.Stereographic(central_lat,central_lon,false_easting=None,false_northing=None,true_scale_lat=None,ellipsoid=None,scale_factor_at_projection_origin=None)[source]#Constructs a Stereographic coord system.

- Parameters

central_lat(float) – The latitude of the pole.

central_lon(float) – The central longitude, which aligns with the y axis.

false_easting(float,optional) – X offset from planar origin in metres.

false_northing(float,optional) – Y offset from planar origin in metres.

true_scale_lat(float,optional) – Latitude of true scale.

scale_factor_at_projection_origin(float,optional) – Scale factor at the origin of the projection

ellipsoid(`GeogCS`

, optional) – If given, defines the ellipsoid.Notes

It is only valid to provide one of true_scale_lat and scale_factor_at_projection_origin

- __eq__(
other)#Override equality

- as_cartopy_projection()[source]#
Return a cartopy projection representing our native map.

`as_cartopy_crs()`

for map projections but for spherical coord systems (which are not map projections) we use a map projection, such as PlateCarree.

- xml_element(
doc,attrs=None)#Default behaviour for coord systems.

- central_lat#
True latitude of planar origin in degrees.

- central_lon#
True longitude of planar origin in degrees.

- false_easting#
X offset from planar origin in metres.

- false_northing#
Y offset from planar origin in metres.

- grid_mapping_name
= 'stereographic'#

- scale_factor_at_projection_origin#
Scale factor at projection origin.

- true_scale_lat#
Latitude of true scale.

A cylindrical map projection, with XY coordinates measured in metres.

classiris.coord_systems.TransverseMercator(latitude_of_projection_origin,longitude_of_central_meridian,false_easting=None,false_northing=None,scale_factor_at_central_meridian=None,ellipsoid=None)[source]#Constructs a TransverseMercator object.

Args:

- latitude_of_projection_origin:
True latitude of planar origin in degrees.

- longitude_of_central_meridian:
True longitude of planar origin in degrees.

Kwargs:

- false_easting:
X offset from planar origin in metres. Defaults to 0.0 .

- false_northing:
Y offset from planar origin in metres. Defaults to 0.0 .

- scale_factor_at_central_meridian:
Reduces the cylinder to slice through the ellipsoid (secant form). Used to provide TWO longitudes of zero distortion in the area of interest. Defaults to 1.0 .

- ellipsoid (
`GeogCS`

):If given, defines the ellipsoid.

Example:

airy1830 = GeogCS(6377563.396, 6356256.909) osgb = TransverseMercator(49, -2, 400000, -100000, 0.9996012717, ellipsoid=airy1830)

- __eq__(
other)#Override equality

- as_cartopy_projection()[source]#
Return a cartopy projection representing our native map.

`as_cartopy_crs()`

for map projections but for spherical coord systems (which are not map projections) we use a map projection, such as PlateCarree.

- xml_element(
doc,attrs=None)#Default behaviour for coord systems.

- false_easting#
X offset from planar origin in metres.

- false_northing#
Y offset from planar origin in metres.

- grid_mapping_name
= 'transverse_mercator'#

- latitude_of_projection_origin#
True latitude of planar origin in degrees.

- longitude_of_central_meridian#
True longitude of planar origin in degrees.

- scale_factor_at_central_meridian#
Scale factor at the centre longitude.

A vertical/near-side perspective satellite image map projection.

classiris.coord_systems.VerticalPerspective(latitude_of_projection_origin,longitude_of_projection_origin,perspective_point_height,false_easting=None,false_northing=None,ellipsoid=None)[source]#Constructs a Vertical Perspective coord system.

Args:

- latitude_of_projection_origin:
True latitude of planar origin in degrees.

- longitude_of_projection_origin:
True longitude of planar origin in degrees.

- perspective_point_height:
Altitude of satellite in metres above the surface of the ellipsoid.

Kwargs:

- false_easting:
X offset from planar origin in metres. Defaults to 0.0 .

- false_northing:
Y offset from planar origin in metres. Defaults to 0.0 .

- ellipsoid (
`GeogCS`

):If given, defines the ellipsoid.

- __eq__(
other)#Override equality

- as_cartopy_projection()[source]#
Return a cartopy projection representing our native map.

`as_cartopy_crs()`

for map projections but for spherical coord systems (which are not map projections) we use a map projection, such as PlateCarree.

- xml_element(
doc,attrs=None)#Default behaviour for coord systems.

- false_easting#
X offset from planar origin in metres.

- false_northing#
Y offset from planar origin in metres.

- grid_mapping_name
= 'vertical_perspective'#

- latitude_of_projection_origin#
True latitude of planar origin in degrees.

- longitude_of_projection_origin#
True longitude of planar origin in degrees.

- perspective_point_height#
Altitude of satellite in metres.