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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)

Bases: iris.coord_systems.CoordSystem

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)
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)
as_cartopy_crs()
as_cartopy_globe()
as_cartopy_projection()
xml_element(doc)
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 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)

Bases: iris.coord_systems.CoordSystem

Constructs a LambertConformal coord system.

Args:

  • 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.

Kwargs:

  • secant_latitudes

    Latitudes of secant intersection.

  • ellipsoid

    GeogCS defining the ellipsoid.

as_cartopy_crs()
as_cartopy_projection()
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'
secant_latitudes = None

Latitudes of secant intersection.

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A Specific transverse mercator projection on a specific ellipsoid.

class iris.coord_systems.OSGB

Bases: iris.coord_systems.TransverseMercator

A Specific transverse mercator projection on a specific ellipsoid.

as_cartopy_crs()
as_cartopy_projection()
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)

Bases: iris.coord_systems.CoordSystem

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.

  • false_easting

    X offset from planar origin in metres. Defaults to 0.

  • false_northing

    Y offset from planar origin in metres. Defaults to 0.

Kwargs:

  • ellipsoid

    GeogCS defining the ellipsoid.

as_cartopy_crs()
as_cartopy_projection()
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)

Bases: iris.coord_systems.CoordSystem

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()
as_cartopy_projection()
xml_element(doc)
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)

Bases: iris.coord_systems.CoordSystem

Constructs a Stereographic coord system.

Args:

  • central_lat

    The latitude of the pole.

  • central_lon

    The central longitude, which aligns with the y axis.

  • false_easting

    X offset from planar origin in metres. Defaults to 0.

  • false_northing

    Y offset from planar origin in metres. Defaults to 0.

Kwargs:

  • true_scale_lat

    Latitude of true scale.

  • ellipsoid

    GeogCS defining the ellipsoid.

as_cartopy_crs()
as_cartopy_projection()
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)

Bases: iris.coord_systems.CoordSystem

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:

  • ellipsoid

    Optional GeogCS defining the ellipsoid.

Example:

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

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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)

Bases: iris.coord_systems.CoordSystem

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.

  • false_easting

    X offset from planar origin in metres. Defaults to 0.

  • false_northing

    Y offset from planar origin in metres. Defaults to 0.

Kwargs:

  • ellipsoid

    GeogCS defining the ellipsoid.

as_cartopy_crs()
as_cartopy_projection()
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.

test_fe = None

X offset from planar origin in metres.

test_fn = None

Y offset from planar origin in metres.

test_pph = None

Altitude of satellite in metres.

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