Source code for satpy.readers.avhrr_l1b_gaclac

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (c) 2009-2019 Satpy developers
# This file is part of satpy.
# satpy 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.
# satpy 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
# satpy.  If not, see <>.
"""Reading and calibrating GAC and LAC AVHRR data.

Uses Pygac under the hood. See the `Pygac Documentation`_ for supported data
formats as well as calibration and navigation methods.

.. todo::

    Fine grained calibration
    Radiance output

.. _Pygac Documentation:

import logging
from datetime import datetime, timedelta

import dask.array as da
import numpy as np
import pygac.utils
import xarray as xr
from pygac.gac_klm import GACKLMReader
from pygac.gac_pod import GACPODReader
from pygac.lac_klm import LACKLMReader
from pygac.lac_pod import LACPODReader

from satpy.readers.file_handlers import BaseFileHandler
from satpy.utils import get_legacy_chunk_size

logger = logging.getLogger(__name__)

CHUNK_SIZE = get_legacy_chunk_size()

spacecrafts = {7: "NOAA 15", 3: "NOAA 16", 13: "NOAA 18", 15: "NOAA 19"}

AVHRR3_CHANNEL_NAMES = {"1": 0, "2": 1, "3A": 2, "3B": 3, "4": 4, "5": 5}
AVHRR2_CHANNEL_NAMES = {"1": 0, "2": 1, "3": 2, "4": 3, "5": 4}
AVHRR_CHANNEL_NAMES = {"1": 0, "2": 1, "3": 2, "4": 3}
ANGLES = ('sensor_zenith_angle', 'sensor_azimuth_angle', 'solar_zenith_angle',
          'solar_azimuth_angle', 'sun_sensor_azimuth_difference_angle')

[docs] class GACLACFile(BaseFileHandler): """Reader for GAC and LAC data.""" def __init__(self, filename, filename_info, filetype_info, start_line=None, end_line=None, strip_invalid_coords=True, interpolate_coords=True, **reader_kwargs): """Init the file handler. Args: start_line: User defined start scanline end_line: User defined end scanline strip_invalid_coords: Strip scanlines with invalid coordinates in the beginning/end of the orbit interpolate_coords: Interpolate coordinates from every eighth pixel to all pixels. reader_kwargs: More keyword arguments to be passed to pygac.Reader. See the pygac documentation for available options. """ super(GACLACFile, self).__init__( filename, filename_info, filetype_info) self.start_line = start_line self.end_line = end_line self.strip_invalid_coords = strip_invalid_coords self.interpolate_coords = interpolate_coords self.reader_kwargs = reader_kwargs self.creation_site = filename_info.get('creation_site') self.reader = None self.calib_channels = None self.counts = None self.angles = None self.qual_flags = None self.first_valid_lat = None self.last_valid_lat = None self._start_time = filename_info['start_time'] self._end_time = datetime.combine(filename_info['start_time'].date(), filename_info['end_time'].time()) if self._end_time < self._start_time: self._end_time += timedelta(days=1) self.platform_id = filename_info['platform_id'] if self.platform_id in ['NK', 'NL', 'NM', 'NN', 'NP', 'M1', 'M2', 'M3']: if filename_info.get('transfer_mode') == 'GHRR': self.reader_class = GACKLMReader else: self.reader_class = LACKLMReader self.chn_dict = AVHRR3_CHANNEL_NAMES self.sensor = 'avhrr-3' elif self.platform_id in ['NC', 'ND', 'NF', 'NH', 'NJ']: if filename_info.get('transfer_mode') == 'GHRR': self.reader_class = GACPODReader else: self.reader_class = LACPODReader self.chn_dict = AVHRR2_CHANNEL_NAMES self.sensor = 'avhrr-2' else: if filename_info.get('transfer_mode') == 'GHRR': self.reader_class = GACPODReader else: self.reader_class = LACPODReader self.chn_dict = AVHRR_CHANNEL_NAMES self.sensor = 'avhrr' self.filename_info = filename_info
[docs] def read_raw_data(self): """Create a pygac reader and read raw data from the file.""" if self.reader is None: self.reader = self.reader_class( interpolate_coords=self.interpolate_coords, creation_site=self.creation_site, **self.reader_kwargs) if np.all(self.reader.mask): raise ValueError('All data is masked out')
[docs] def get_dataset(self, key, info): """Get the dataset.""" self.read_raw_data() if key['name'] in ['latitude', 'longitude']: # Lats/lons are buffered by the reader if key['name'] == 'latitude': _, data = self.reader.get_lonlat() else: data, _ = self.reader.get_lonlat() # If coordinate interpolation is disabled, only every eighth # pixel has a lat/lon coordinate xdim = 'x' if self.interpolate_coords else 'x_every_eighth' xcoords = None elif key['name'] in ANGLES: data = self._get_angle(key) xdim = 'x' if self.interpolate_coords else 'x_every_eighth' xcoords = None elif key['name'] == 'qual_flags': data = self.reader.get_qual_flags() xdim = 'num_flags' xcoords = ['Scan line number', 'Fatal error flag', 'Insufficient data for calibration', 'Insufficient data for calibration', 'Solar contamination of blackbody in channels 3', 'Solar contamination of blackbody in channels 4', 'Solar contamination of blackbody in channels 5'] elif key['name'].upper() in self.chn_dict: # Read and calibrate channel data data = self._get_channel(key) xdim = 'x' xcoords = None else: raise ValueError('Unknown dataset: {}'.format(key['name'])) # Update start/end time using the actual scanline timestamps times = self.reader.get_times() self._start_time = times[0].astype(datetime) self._end_time = times[-1].astype(datetime) # Select user-defined scanlines and/or strip invalid coordinates if (self.start_line is not None or self.end_line is not None or self.strip_invalid_coords): data, times = self.slice(data=data, times=times) # Create data array chunk_cols = data.shape[1] chunk_lines = int((CHUNK_SIZE ** 2) / chunk_cols) res = xr.DataArray(da.from_array(data, chunks=(chunk_lines, chunk_cols)), dims=['y', xdim], attrs=info) if xcoords: res[xdim] = xcoords # Update dataset attributes self._update_attrs(res) # Add scanline acquisition times res['acq_time'] = ('y', times) res['acq_time'].attrs['long_name'] = 'Mean scanline acquisition time' return res
[docs] def slice(self, data, times): """Select user-defined scanlines and/or strip invalid coordinates. Furthermore, update scanline timestamps. Args: data: Data to be sliced times: Scanline timestamps Returns: Sliced data and timestamps """ sliced = self._slice(data) times = self._slice(times) self._start_time = times[0].astype(datetime) self._end_time = times[-1].astype(datetime) return sliced, times
[docs] def _slice(self, data): """Select user-defined scanlines and/or strip invalid coordinates. Returns: Sliced data """ start_line = self.start_line if self.start_line is not None else 0 end_line = self.end_line if self.end_line is not None else 0 # Strip scanlines with invalid coordinates if self.strip_invalid_coords: first_valid_lat, last_valid_lat = self._strip_invalid_lat() else: first_valid_lat = last_valid_lat = None # Check and correct user-defined scanlines, if possible start_line, end_line = pygac.utils.check_user_scanlines( start_line=start_line, end_line=end_line, first_valid_lat=first_valid_lat, last_valid_lat=last_valid_lat, along_track=data.shape[0] ) # Slice data sliced = pygac.utils.slice_channel(data, start_line=start_line, end_line=end_line, first_valid_lat=first_valid_lat, last_valid_lat=last_valid_lat) if isinstance(sliced, tuple): # pygac < 1.4.0 sliced = sliced[0] return sliced
[docs] def _get_channel(self, key): """Get channel and buffer results.""" name = key['name'] calibration = key['calibration'] if calibration == 'counts': if self.counts is None: counts = self.reader.get_counts() self.counts = counts channels = self.counts elif calibration in ['reflectance', 'brightness_temperature']: if self.calib_channels is None: self.calib_channels = self.reader.get_calibrated_channels() channels = self.calib_channels else: raise ValueError('Unknown calibration: {}'.format(calibration)) return channels[:, :, self.chn_dict[name.upper()]]
[docs] def _get_qual_flags(self): """Get quality flags and buffer results.""" if self.qual_flags is None: self.qual_flags = self.reader.get_qual_flags() return self.qual_flags
[docs] def _get_angle(self, key): """Get angles and buffer results.""" if self.angles is None: sat_azi, sat_zenith, sun_azi, sun_zenith, rel_azi = self.reader.get_angles() self.angles = {'sensor_zenith_angle': sat_zenith, 'sensor_azimuth_angle': sat_azi, 'solar_zenith_angle': sun_zenith, 'solar_azimuth_angle': sun_azi, 'sun_sensor_azimuth_difference_angle': rel_azi} return self.angles[key['name']]
[docs] def _strip_invalid_lat(self): """Strip scanlines with invalid coordinates in the beginning/end of the orbit. Returns: First and last scanline with valid latitudes. """ if self.first_valid_lat is None: _, lats = self.reader.get_lonlat() start, end = pygac.utils.strip_invalid_lat(lats) self.first_valid_lat, self.last_valid_lat = start, end return self.first_valid_lat, self.last_valid_lat
[docs] def _update_attrs(self, res): """Update dataset attributes.""" for attr in self.reader.meta_data: res.attrs[attr] = self.reader.meta_data[attr] res.attrs['platform_name'] = self.reader.spacecraft_name res.attrs['orbit_number'] = self.filename_info.get('orbit_number', None) res.attrs['sensor'] = self.sensor try: res.attrs['orbital_parameters'] = {'tle': self.reader.get_tle_lines()} except (IndexError, RuntimeError): pass
@property def start_time(self): """Get the start time.""" return self._start_time @property def end_time(self): """Get the end time.""" return self._end_time