Source code for polar2grid.filters._utils
#!/usr/bin/env python
# encoding: utf-8
# Copyright (C) 2021 Space Science and Engineering Center (SSEC),
# University of Wisconsin-Madison.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
# This file is part of the polar2grid software package. Polar2grid takes
# satellite observation data, remaps it, and writes it to a file format for
# input into another program.
# Documentation: http://www.ssec.wisc.edu/software/polar2grid/
"""Utilities related to filtering."""
import logging
import dask.array as da
import numpy as np
try:
# Python 3.9+
from functools import cache
except ImportError:
from functools import lru_cache as cache
from typing import Union
from pyresample.boundary import AreaBoundary, AreaDefBoundary, Boundary
from pyresample.geometry import AreaDefinition, SwathDefinition, get_geostationary_bounding_box_in_lonlats
from pyresample.spherical import SphPolygon
logger = logging.getLogger(__name__)
PRGeometry = Union[SwathDefinition, AreaDefinition]
[docs]
def boundary_for_area(area_def: PRGeometry) -> Boundary:
"""Create Boundary object representing the provided area."""
if getattr(area_def, "is_geostationary", False):
adp = Boundary(*get_geostationary_bounding_box_in_lonlats(area_def, nb_points=100))
else:
freq_fraction = 0.30 if isinstance(area_def, AreaDefinition) else 0.05
try:
adp = area_def.boundary()
adp.decimate(int(freq_fraction * area_def.shape[0]))
except ValueError:
if not isinstance(area_def, SwathDefinition):
logger.error("Unable to generate bounding geolocation polygon")
raise
logger.warning(
"Geolocation data contains invalid bounding values. Computing entire array to get bounds instead."
)
adp = _compute_boundary_from_whole_swath(area_def)
return adp
[docs]
def _compute_boundary_from_whole_swath(swath_def: SwathDefinition):
lons, lats = swath_def.get_lonlats()
min_lon = np.nanmin(lons)
max_lon = np.nanmax(lons)
min_lat = np.nanmin(lats)
max_lat = np.nanmax(lats)
min_lon, max_lon, min_lat, max_lat = da.compute(min_lon, max_lon, min_lat, max_lat)
x_passes_antimeridian = (max_lon - min_lon) > 355
epsilon = 0.1
y_is_pole = (max_lat >= 90 - epsilon) or (min_lat <= -90 + epsilon)
if x_passes_antimeridian and not y_is_pole:
wrapped_lons = lons % 360
min_lon, max_lon = da.compute(np.nanmin(wrapped_lons), np.nanmax(wrapped_lons))
max_lon -= 360
sides = (
([min_lon, max_lon], [max_lat, max_lat]), # top
([max_lon, max_lon], [max_lat, min_lat]), # right
([max_lon, min_lon], [min_lat, min_lat]), # bot
([min_lon, max_lon], [min_lat, max_lat]), # left
)
return AreaBoundary(*sides)
[docs]
@cache
def polygon_for_area(area_def: PRGeometry) -> SphPolygon:
boundary = boundary_for_area(area_def)
return boundary.contour_poly