Readers

SatPy supports reading and loading data from many input file formats and schemes. The Scene object provides a simple interface around all the complexity of these various formats through its load method. The following sections describe the different way data can be loaded, requested, or added to a Scene object.

Available Readers

To get a list of available readers use the available_readers function:

>>> from satpy import available_readers
>>> available_readers()

Filter loaded files

Coming soon…

Load data

Datasets in SatPy are identified by certain pieces of metadata set during data loading. These include name, wavelength, calibration, resolution, polarization, and modifiers. Normally, once a Scene is created requesting datasets by name or wavelength is all that is needed:

>>> from satpy import Scene
>>> scn = Scene(reader="hrit_msg", filenames=filenames)
>>> scn.load([0.6, 0.8, 10.8])
>>> scn.load(['IR_120', 'IR_134'])

However, in many cases datasets are available in multiple spatial resolutions, multiple calibrations (brightness_temperature, reflectance, radiance, etc), multiple polarizations, or have corrections or other modifiers already applied to them. By default SatPy will provide the version of the dataset with the highest resolution and the highest level of calibration (brightness temperature or reflectance over radiance). It is also possible to request one of these exact versions of a dataset by using the DatasetID class:

>>> from satpy import DatasetID
>>> my_channel_id = DatasetID(name='IR_016', calibration='radiance')
>>> scn.load([my_channel_id])
>>> print(scn['IR_016'])

Or request multiple datasets at a specific calibration, resolution, or polarization:

>>> scn.load([0.6, 0.8], resolution=1000)

Or multiple calibrations:

>>> scn.load([0.6, 10.8], calibrations=['brightness_temperature', 'radiance'])

In the above case SatPy will load whatever dataset is available and matches the specified parameters. So the above load call would load the 0.6 (a visible/reflectance band) radiance data and 10.8 (an IR band) brightness temperature data.

Note

If a dataset could not be loaded there is no exception raised. You must check the scn.missing_datasets property for any DatasetID that could not be loaded.

To find out what datasets are available from a reader from the files that were provided to the Scene use available_dataset_ids():

>>> scn.available_dataset_ids()

Or available_dataset_names() for just the string names of Datasets:

>>> scn.available_dataset_names()

Search for local files

SatPy provides a utility find_files_and_readers() for searching for files in a base directory matching various search parameters. This function discovers files based on filename patterns. It returns a dictionary mapping reader name to a list of filenames supported. This dictionary can be passed directly to the Scene initialization.

>>> from satpy import find_files_and_readers, Scene
>>> from datetime import datetime
>>> my_files = find_files_and_readers(base_dir='/data/viirs_sdrs',
...                                   reader='viirs_sdr',
...                                   start_time=datetime(2017, 5, 1, 18, 1, 0),
...                                   end_time=datetime(2017, 5, 1, 18, 30, 0))
>>> scn = Scene(filenames=my_files)

See the find_files_and_readers() documentation for more information on the possible parameters.

Adding a Reader to SatPy

This is described in the developer guide, see Adding a Custom Reader to SatPy

Implemented readers

xRIT-based readers

HRIT/LRIT format reader

This module is the base module for all HRIT-based formats. Here, you will find the common building blocks for hrit reading.

One of the features here is the on-the-fly decompression of hrit files. It needs a path to the xRITDecompress binary to be provided through the environment variable called XRIT_DECOMPRESS_PATH. When compressed hrit files are then encountered (files finishing with .C_), they are decompressed to the system’s temporary directory for reading.

SEVIRI HRIT format reader

References

  • MSG Level 1.5 Image Data Format Description
  • Radiometric Calibration of MSG SEVIRI Level 1.5 Image Data in Equivalent Spectral Blackbody Radiance

HRIT format reader for JMA data

References

JMA HRIT - Mission Specific Implementation http://www.jma.go.jp/jma/jma-eng/satellite/introduction/4_2HRIT.pdf

GOES HRIT format reader

References

LRIT/HRIT Mission Specific Implementation, February 2012 GVARRDL98.pdf 05057_SPE_MSG_LRIT_HRI

HRIT format reader

References

ELECTRO-L GROUND SEGMENT MSU-GS INSTRUMENT,
LRIT/HRIT Mission Specific Implementation, February 2012