unifhy.RotatedLatLonGrid.from_field

classmethod RotatedLatLonGrid.from_field(field)

Instantiate a RotatedLatLonGrid from spatial dimension coordinates of a cf.Field.

Parameters

field: cf.Field

The field object that will be used to instantiate a RotatedLatLonGrid instance. This field must feature a ‘grid_latitude’ and a ‘grid_longitude’ dimension coordinates, and these must feature bounds. In addition, the parameters required for the conversion of the grid to a true latitude-longitude reference system must be set (i.e. grid_north_pole_latitude, grid_north_pole_longitude, and optional north_pole_grid_longitude).

Returns

RotatedLatLonGrid

Examples

Instantiating from a 2D field:

>>> import cf
>>> f = cf.Field()
>>> lat = f.set_construct(
...     cf.DimensionCoordinate(
...         properties={'standard_name': 'grid_latitude',
...                     'units': 'degrees',
...                     'axis': 'Y'},
...         data=cf.Data([-0.88, -0.44, 0., 0.44, 0.88]),
...         bounds=cf.Bounds(data=cf.Data([[-1.1, -0.66], [-0.66, -0.22],
...                                        [-0.22, 0.22], [0.22, 0.66],
...                                        [0.66, 1.1]]))
...     ),
...     axes=f.set_construct(cf.DomainAxis(size=5))
... )
>>> lon = f.set_construct(
...     cf.DimensionCoordinate(
...         properties={'standard_name': 'grid_longitude',
...                     'units': 'degrees',
...                     'axis': 'X'},
...         data=cf.Data([-2.5, -2.06, -1.62, -1.18]),
...         bounds=cf.Bounds(data=cf.Data([[-2.72, -2.28], [-2.28, -1.84],
...                                        [-1.84, -1.4], [-1.4, -0.96]]))
...     ),
...     axes=f.set_construct(cf.DomainAxis(size=4))
... )
>>> crs = f.set_construct(
...     cf.CoordinateReference(
...         coordinate_conversion=cf.CoordinateConversion(
...             parameters={'grid_mapping_name': 'rotated_latitude_longitude',
...                         'grid_north_pole_latitude': 38.0,
...                         'grid_north_pole_longitude': 190.0}),
...         coordinates=(lat, lon)
...     )
... )
>>> sd = RotatedLatLonGrid.from_field(f)
>>> print(sd)
RotatedLatLonGrid(
    shape {Y, X}: (5, 4)
    Y, grid_latitude (5,): [-0.88, ..., 0.88] degrees
    X, grid_longitude (4,): [-2.5, ..., -1.18] degrees
    Y_bounds (5, 2): [[-1.1, ..., 1.1]] degrees
    X_bounds (4, 2): [[-2.72, ..., -0.96]] degrees
)

Using the field interface back and forth:

>>> sd1 = RotatedLatLonGrid.from_extent_and_resolution(
...     grid_latitude_extent=(-1.1, 1.1),
...     grid_longitude_extent=(-2.72, -0.96),
...     grid_latitude_resolution=0.44,
...     grid_longitude_resolution=0.44,
...     grid_north_pole_latitude=38.0,
...     grid_north_pole_longitude=190.0
... )
>>> sd2 = RotatedLatLonGrid.from_field(sd1.to_field())
>>> sd2 == sd1
True