satpy.readers.utils module

Helper functions for satpy readers.

satpy.readers.utils.apply_earthsun_distance_correction(reflectance, utc_date=None)

Correct reflectance data to account for changing Earth-Sun distance.

satpy.readers.utils.apply_rad_correction(data, slope, offset)

Apply GSICS-like correction factors to radiance data.

satpy.readers.utils.bbox(img)

Find the bounding box around nonzero elements in the given array.

Copied from https://stackoverflow.com/a/31402351/5703449 .

Returns

rowmin, rowmax, colmin, colmax

satpy.readers.utils.generic_open(filename, *args, **kwargs)

Context manager for opening either a regular file or a bzip2 file.

Returns a file-like object.

satpy.readers.utils.get_array_date(scn_data, utc_date=None)

Get start time from a channel data array.

satpy.readers.utils.get_earth_radius(lon, lat, a, b)

Compute radius of the earth ellipsoid at the given longitude and latitude.

Parameters

• lon – Geodetic longitude (degrees)

• lat – Geodetic latitude (degrees)

• a – Semi-major axis of the ellipsoid (meters)

• b – Semi-minor axis of the ellipsoid (meters)

Returns

Earth Radius (meters)

satpy.readers.utils.get_geostationary_angle_extent(geos_area)

Get the max earth (vs space) viewing angles in x and y.

satpy.readers.utils.get_geostationary_bounding_box(geos_area, nb_points=50)

Get the bbox in lon/lats of the valid pixels inside geos_area.

Parameters

• geos_area – The geostationary area to analyse.

• nb_points – Number of points on the polygon

satpy.readers.utils.get_geostationary_mask(area, chunks=None)

Compute a mask of the earth’s shape as seen by a geostationary satellite.

Parameters

• area (pyresample.geometry.AreaDefinition) – Corresponding area definition

• chunks (int or tuple) – Chunk size for the 2D array that is generated.

Returns

Boolean mask, True inside the earth’s shape, False outside.

satpy.readers.utils.get_sub_area(area, xslice, yslice)

Apply slices to the area_extent and size of the area.

satpy.readers.utils.get_user_calibration_factors(band_name, correction_dict)

Retrieve radiance correction factors from user-supplied dict.

satpy.readers.utils.np2str(value)

Convert an numpy.string_ to str.

Parameters

value (ndarray) – scalar or 1-element numpy array to convert

Raises

ValueError – if value is array larger than 1-element or it is not of type numpy.string_ or it is not a numpy array

satpy.readers.utils.reduce_mda(mda, max_size=100)

Recursively remove arrays with more than max_size elements from the given metadata dictionary.

satpy.readers.utils.remove_earthsun_distance_correction(reflectance, utc_date=None)

Remove the sun-earth distance correction.

satpy.readers.utils.unzip_context(filename)

Context manager for decompressing a .bz2 file on the fly.

Uses unzip_file. Removes the uncompressed file on exit of the context manager.

Returns: the filename of the uncompressed file or of the original file if it was not compressed.

satpy.readers.utils.unzip_file(filename, prefix=None)

Unzip the file ending with ‘bz2’. Initially with pbzip2 if installed or bz2.

Parameters

• filename – The file to unzip.

• prefix (str, optional) – If file is one of many segments of data, prefix random filename

• number. (for correct sorting. This is normally the segment) –

Returns

Temporary filename path for decompressed file or None.