satpy.readers.seviri_l1b_native module

SEVIRI native format reader.

References

• MSG Level 1.5 Native Format File Definition

class satpy.readers.seviri_l1b_native.ImageBoundaries(header, trailer, mda)

Bases: object

Collect image boundary information.

Initialize the class.

get_img_bounds(dataset_id, is_roi)

Get image line and column boundaries.

Returns

Dictionary with the four keys ‘south_bound’, ‘north_bound’, ‘east_bound’ and ‘west_bound’, each containing a list of the respective line/column numbers of the image boundaries.

Lists (rather than scalars) are returned since the HRV data in FES mode contain data from two windows/areas.

class satpy.readers.seviri_l1b_native.NativeMSGFileHandler(filename, filename_info, filetype_info, calib_mode='nominal', fill_disk=False, ext_calib_coefs=None, include_raw_metadata=False, mda_max_array_size=100)

Bases: BaseFileHandler

SEVIRI native format reader.

Calibration

See satpy.readers.seviri_base.

Padding channel data to full disk

By providing the fill_disk as True in the reader_kwargs, the channel is loaded as full disk, padded with no-data where necessary. This is especially useful for the HRV channel, but can also be used for RSS and ROI data. By default the original, unpadded, data are loaded:

scene = satpy.Scene(filenames,
                    reader='seviri_l1b_native',
                    reader_kwargs={'fill_disk': False})

Metadata

See satpy.readers.seviri_base.

Initialize the reader.

calibrate(data, dataset_id)

Calibrate the data.

property end_time

Get the general end time for this file.

get_area_def(dataset_id)

Get the area definition of the band.

In general, image data from one window/area is available. For the HRV channel in FES mode, however, data from two windows (‘Lower’ and ‘Upper’) are available. Hence, we collect lists of area-extents and corresponding number of image lines/columns. In case of FES HRV data, two area definitions are computed, stacked and squeezed. For other cases, the lists will only have one entry each, from which a single area definition is computed.

Note that the AreaDefinition area extents returned by this function for Native data will be slightly different compared to the area extents returned by the SEVIRI HRIT reader. This is due to slightly different pixel size values when calculated using the data available in the files. E.g. for the 3 km grid:

Native: data15hd['ImageDescription']['ReferenceGridVIS_IR']['ColumnDirGridStep'] == 3000.4031658172607 HRIT:                            np.deg2rad(2.**16 / pdict['lfac']) * pdict['h'] == 3000.4032785810186

This results in the Native 3 km full-disk area extents being approx. 20 cm shorter in each direction.

The method for calculating the area extents used by the HRIT reader (CFAC/LFAC mechanism) keeps the highest level of numeric precision and is used as reference by EUM. For this reason, the standard area definitions defined in the areas.yaml file correspond to the HRIT ones.

get_area_extent(dataset_id)

Get the area extent of the file.

Until December 2017, the data is shifted by 1.5km SSP North and West against the nominal GEOS projection. Since December 2017 this offset has been corrected. A flag in the data indicates if the correction has been applied. If no correction was applied, adjust the area extent to match the shifted data.

For more information see Section 3.1.4.2 in the MSG Level 1.5 Image Data Format Description. The correction of the area extent is documented in a developer’s memo.

get_dataset(dataset_id, dataset_info)

Get the dataset.

is_roi()

Check if data covers a selected region of interest (ROI).

Standard RSS data consists of 3712 columns and 1392 lines, covering the three northmost segements of the SEVIRI disk. Hence, if the data does not cover the full disk, nor the standard RSS region in RSS mode, it’s assumed to be ROI data.

property nominal_end_time

Read the repeat cycle nominal end time from metadata.

property nominal_start_time

Read the repeat cycle nominal start time from metadata.

property observation_end_time

Read the repeat cycle sensing end time from metadata.

property observation_start_time

Read the repeat cycle sensing start time from metadata.

property satpos

Get actual satellite position in geodetic coordinates (WGS-84).

Evaluate orbit polynomials at the start time of the scan.

Returns: Longitude [deg east], Latitude [deg north] and Altitude [m]

property start_time

Get general start time for this file.

class satpy.readers.seviri_l1b_native.Padder(dataset_id, img_bounds, is_full_disk)

Bases: object

Padding of HRV, RSS and ROI data to full disk.

Initialize the padder.

pad_data(dataset)

Pad data to full disk with empty pixels.

satpy.readers.seviri_l1b_native.get_available_channels(header)

Get the available channels from the header information.