# iris.coord_systems¶

Definitions of coordinate systems.

In this module:

Abstract base class for coordinate systems.

class `iris.coord_systems.``CoordSystem`

Bases: `object`

Abstract base class for coordinate systems.

`as_cartopy_crs`()

Return a cartopy CRS representing our native coordinate system.

`as_cartopy_projection`()

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.

`grid_mapping_name` = None

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

class `iris.coord_systems.``GeogCS`(semi_major_axis=None, semi_minor_axis=None, inverse_flattening=None, longitude_of_prime_meridian=0)

Creates a new GeogCS.

Kwargs:

• semi_major_axis - of ellipsoid in metres
• semi_minor_axis - of ellipsoid in metres
• inverse_flattening - of ellipsoid
• longitude_of_prime_meridian - Can be used to specify the
prime meridian on the ellipsoid in degrees. Default = 0.

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 calulated from the formula:

Currently, Iris will not allow over-specification (all three ellipsoid paramaters). Examples:

```cs = GeogCS(6371229)
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)
```
`as_cartopy_crs`()

Return a cartopy CRS representing our native coordinate system.

`as_cartopy_globe`()
`as_cartopy_projection`()

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)

Default behaviour for coord systems.

`grid_mapping_name` = 'latitude_longitude'
`inverse_flattening` = None

where

`longitude_of_prime_meridian` = None

Describes ‘zero’ on the ellipsoid in degrees.

`semi_major_axis` = None

Major radius of the ellipsoid in metres.

`semi_minor_axis` = None

Minor radius of the ellipsoid in metres.

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A coordinate system in the Lambert Azimuthal Equal Area projection.

class `iris.coord_systems.``LambertAzimuthalEqualArea`(latitude_of_projection_origin=0.0, longitude_of_projection_origin=0.0, false_easting=0.0, false_northing=0.0, ellipsoid=None)

Constructs a Lambert Azimuthal Equal Area coord system.

Kwargs:

• latitude_of_projection_origin
True latitude of planar origin in degrees. Defaults to 0.
• longitude_of_projection_origin
True longitude of planar origin in degrees. Defaults to 0.
• false_easting
X offset from planar origin in metres. Defaults to 0.
• false_northing
Y offset from planar origin in metres. Defaults to 0.
• ellipsoid
`GeogCS` defining the ellipsoid.
`as_cartopy_crs`()

Return a cartopy CRS representing our native coordinate system.

`as_cartopy_projection`()

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.

`ellipsoid` = None

Ellipsoid definition.

`false_easting` = None

X offset from planar origin in metres.

`false_northing` = None

Y offset from planar origin in metres.

`grid_mapping_name` = 'lambert_azimuthal_equal_area'
`latitude_of_projection_origin` = None

True latitude of planar origin in degrees.

`longitude_of_projection_origin` = None

True longitude of planar origin in degrees.

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A coordinate system in the Lambert Conformal conic projection.

class `iris.coord_systems.``LambertConformal`(central_lat=39.0, central_lon=-96.0, false_easting=0.0, false_northing=0.0, secant_latitudes=(33, 45), ellipsoid=None)

Constructs a LambertConformal coord system.

Kwargs:

• central_lat
The latitude of “unitary scale”.
• central_lon
The central longitude.
• false_easting
X offset from planar origin in metres.
• false_northing
Y offset from planar origin in metres.
• secant_latitudes
Latitudes of secant intersection.
• ellipsoid
`GeogCS` defining the ellipsoid.
`as_cartopy_crs`()

Return a cartopy CRS representing our native coordinate system.

`as_cartopy_projection`()

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.

`central_lat` = None

True latitude of planar origin in degrees.

`central_lon` = None

True longitude of planar origin in degrees.

`ellipsoid` = None

Ellipsoid definition.

`false_easting` = None

X offset from planar origin in metres.

`false_northing` = None

Y offset from planar origin in metres.

`grid_mapping_name` = 'lambert_conformal_conic'

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A coordinate system in the Mercator projection.

class `iris.coord_systems.``Mercator`(longitude_of_projection_origin=0, ellipsoid=None)

Constructs a Mercator coord system.

Kwargs:
• longitude_of_projection_origin
True longitude of planar origin in degrees.
• ellipsoid
`GeogCS` defining the ellipsoid.
`as_cartopy_crs`()

Return a cartopy CRS representing our native coordinate system.

`as_cartopy_projection`()

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.

`ellipsoid` = None

Ellipsoid definition.

`grid_mapping_name` = 'mercator'
`longitude_of_projection_origin` = None

True longitude of planar origin in degrees.

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A Specific transverse mercator projection on a specific ellipsoid.

class `iris.coord_systems.``OSGB`

A Specific transverse mercator projection on a specific ellipsoid.

`as_cartopy_crs`()

Return a cartopy CRS representing our native coordinate system.

`as_cartopy_projection`()

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.

`grid_mapping_name` = 'transverse_mercator'

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An orthographic map projection.

class `iris.coord_systems.``Orthographic`(latitude_of_projection_origin, longitude_of_projection_origin, false_easting=0.0, false_northing=0.0, ellipsoid=None)

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.
• false_northing
Y offset from planar origin in metres. Defaults to 0.
• ellipsoid
`GeogCS` defining the ellipsoid.
`as_cartopy_crs`()

Return a cartopy CRS representing our native coordinate system.

`as_cartopy_projection`()

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.

`ellipsoid` = None

Ellipsoid definition.

`false_easting` = None

X offset from planar origin in metres.

`false_northing` = None

Y offset from planar origin in metres.

`grid_mapping_name` = 'orthographic'
`latitude_of_projection_origin` = None

True latitude of planar origin in degrees.

`longitude_of_projection_origin` = None

True longitude of planar origin in degrees.

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

class `iris.coord_systems.``RotatedGeogCS`(grid_north_pole_latitude, grid_north_pole_longitude, north_pole_grid_longitude=0, ellipsoid=None)

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. Default = 0.
• ellipsoid - Optional `GeogCS` defining
the ellipsoid.

Examples:

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

Return a cartopy CRS representing our native coordinate system.

`as_cartopy_projection`()

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)

Default behaviour for coord systems.

`ellipsoid` = None

Ellipsoid definition.

`grid_mapping_name` = 'rotated_latitude_longitude'
`grid_north_pole_latitude` = None

The true latitude of the rotated pole in degrees.

`grid_north_pole_longitude` = None

The true longitude of the rotated pole in degrees.

`north_pole_grid_longitude` = None

Longitude of true north pole in rotated grid in degrees.

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A stereographic map projection.

class `iris.coord_systems.``Stereographic`(central_lat, central_lon, false_easting=0.0, false_northing=0.0, true_scale_lat=None, ellipsoid=None)

Constructs a Stereographic coord system.

Args:

• central_lat
The latitude of the pole.
• central_lon
The central longitude, which aligns with the y axis.

Kwargs:

• false_easting
X offset from planar origin in metres. Defaults to 0.
• false_northing
Y offset from planar origin in metres. Defaults to 0.
• true_scale_lat
Latitude of true scale.
• ellipsoid
`GeogCS` defining the ellipsoid.
`as_cartopy_crs`()

Return a cartopy CRS representing our native coordinate system.

`as_cartopy_projection`()

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.

`central_lat` = None

True latitude of planar origin in degrees.

`central_lon` = None

True longitude of planar origin in degrees.

`ellipsoid` = None

Ellipsoid definition.

`false_easting` = None

X offset from planar origin in metres.

`false_northing` = None

Y offset from planar origin in metres.

`grid_mapping_name` = 'stereographic'
`true_scale_lat` = None

Latitude of true scale.

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

class `iris.coord_systems.``TransverseMercator`(latitude_of_projection_origin, longitude_of_central_meridian, false_easting, false_northing, scale_factor_at_central_meridian, ellipsoid=None)

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.
• false_easting
X offset from planar origin in metres.
• false_northing
Y offset from planar origin in metres.
• 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.

Kwargs:

Example:

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

Return a cartopy CRS representing our native coordinate system.

`as_cartopy_projection`()

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.

`ellipsoid` = None

Ellipsoid definition.

`false_easting` = None

X offset from planar origin in metres.

`false_northing` = None

Y offset from planar origin in metres.

`grid_mapping_name` = 'transverse_mercator'
`latitude_of_projection_origin` = None

True latitude of planar origin in degrees.

`longitude_of_central_meridian` = None

True longitude of planar origin in degrees.

`scale_factor_at_central_meridian` = None

Reduces the cylinder to slice through the ellipsoid (secant form).

↑ top ↑

An geostationary satellite image map projection.

class `iris.coord_systems.``VerticalPerspective`(latitude_of_projection_origin, longitude_of_projection_origin, perspective_point_height, false_easting=0, false_northing=0, ellipsoid=None)

Constructs an Vertical Perspective 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.

Kwargs:

• false_easting
X offset from planar origin in metres. Defaults to 0.
• false_northing
Y offset from planar origin in metres. Defaults to 0.
• ellipsoid
`GeogCS` defining the ellipsoid.
`as_cartopy_crs`()

Return a cartopy CRS representing our native coordinate system.

`as_cartopy_projection`()

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.

`ellipsoid` = None

Ellipsoid definition.

`grid_mapping_name` = 'vertical_perspective'
`latitude_of_projection_origin` = None

True latitude of planar origin in degrees.

`longitude_of_projection_origin` = None

True longitude of planar origin in degrees.