Adapt avhrr_l1b_gaclac to recent pygac changes

[sfinkens]

Adapt the avhrr_l1b_gaclac reader to the changes introduced by pytroll/pygac#31. This will not be compatible with older pygac versions anymore.

• Allow user to specify the scanline range to be processed
• Allow user to specify TLE dir and name (no PYGAC_CONFIG_FILE needed anymore)
• Make stripping of scanlines with invalid coordinates optional
• Make coordinate interpolation optional
• Make clock drift adjustment optional
• Expose quality flags and some other metadata
• Buffer channels, angles, etc in the file handler
• Refine x dimensions:
  • x for channels, and if interpolate_coords=True also for angles/coordinates
  • num_flags for quality flags
  • x_every_eighth for coordinates/angles if interpolate_coords=False
• Update start_time and end_time using actual scanline timestamps

Example usage:

import satpy
from satpy.utils import logging_on
import logging
logging_on(logging.DEBUG)


def load(filenames, channels):
    scene = satpy.Scene(filenames=filenames, reader='avhrr_l1b_gaclac',
                        reader_kwargs={'start_line': None,
                                       'end_line': None,
                                       'strip_invalid_coords': True,
                                       'adjust_clock_drift': False,
                                       'interpolate_coords': False,
                                       'tle_thresh': 5,
                                       'tle_dir': '/path/to/tle',
                                       'tle_name': 'TLE_%(satname)s.txt'})

    datasets = channels + [
        'solar_zenith_angle',
        'sensor_zenith_angle',
        'solar_azimuth_angle',
        'sensor_azimuth_angle',
        'sun_sensor_azimuth_difference_angle',
        'qual_flags',
        'latitude',
        'longitude'
    ]
    scene.load(datasets)
    for ds in channels:
        scene.show(ds)


filenames = ['input/NSS.GHRR.NJ.D01298.S0157.E0338.B3514748.GC']
channels = ['1', '2', '3', '4', '5']
load(filenames, channels)

channels = ['1', '2', '3a', '3b', '4', '5']
filenames = ['input/NSS.GHRR.NK.D01046.S0614.E0809.B1434546.WI']
load(filenames, channels)

• Require new pygac release in setup.py
• Tests added and test suite added to parent suite
• Tests passed
• Passes flake8 satpy
• Fully documented

[mraspaud]

LGTM

[coveralls]

Coverage increased (+0.5%) to 85.934% when pulling 52e41e6 on sfinkens:feature-avhrr-for-pps into a6ce4df on pytroll:master.

[codecov]

Codecov Report

Merging #935 into master will increase coverage by 0.52%.
The diff coverage is 97.84%.

@@            Coverage Diff             @@
##           master     #935      +/-   ##
==========================================
+ Coverage   85.41%   85.93%   +0.52%     
==========================================
  Files         172      172              
  Lines       26046    26405     +359     
==========================================
+ Hits        22246    22691     +445     
+ Misses       3800     3714      -86

Impacted Files	Coverage Δ
satpy/readers/avhrr_l1b_gaclac.py	94.85% <95.29%> (+4.71%)	⬆️
satpy/tests/reader_tests/test_avhrr_l1b_gaclac.py	97.97% <99.31%> (+2.97%)	⬆️
satpy/readers/nucaps.py	93.71% <0%> (-0.53%)	⬇️
satpy/scene.py	90.35% <0%> (-0.18%)	⬇️
satpy/tests/test_multiscene.py	97.84% <0%> (ø)	⬆️
satpy/multiscene.py	89.13% <0%> (ø)	⬆️
satpy/readers/modis_l2.py	98.52% <0%> (ø)	⬆️
satpy/readers/seviri_l1b_hrit.py	92.3% <0%> (ø)	⬆️
.../tests/reader_tests/test_viirs_edr_active_fires.py	98.75% <0%> (+0.01%)	⬆️
satpy/tests/reader_tests/test_olci_nc.py	95.6% <0%> (+1.31%)	⬆️
... and 3 more

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[mraspaud]

Thanks for the comprehensive work on this reader 👍

[sfinkens]

My pleasure :)