L1B problems

by **OB.DAAC - SeanBailey** » Tue Jul 25, 2017 8:36 pm America/New_York

Correct, the L1B data do not include geolocation information. For that you will need to generate the geolocation file, which SeaDAS is set up to do. This is the same as it is for MODIS. While the L1B for MODIS does include a subsampled geolocation data set, SeaDAS does not use it and expect that the geolocation file to be provided. The generation of spectra for selected pins is no different for VIIRS than it is for MODIS.

Sean

byan0622 · by **byan0622** » Wed Jul 26, 2017 9:30 am America/New_York

This is what happened when we did in SeaDAS:

For MODIS L1B file, when we open spectrum view, the window shows “collecting spectral information” then after a few seconds, the spectrum will show up,
For VIIRS L1B file, when we open spectrum view, it just shows “no spectra selected” and spectrum data does not show up.
Maybe you could help us if we did anything wrong. Thanks.

by **OB SeaDAS - knowles** » Wed Jul 26, 2017 11:00 am America/New_York

I can confirm this as a problem with loading L1B VIIRS files in SeaDAS. In order for the SpectrumView tool which you mentioned to work, bands must have the Spectral Wavelength set. The VIIRS file reader utility inside of the SeaDAS GUI is currently using a default generic function which sets the Spectral Wavelength by parsing it out of the band name (but in the case of VIIRS, the band name does not contain the wavelength). MODIS does have it own spectral wavelength lookup being done (not parsing it from the band name), which is why MODIS L1B files work.

We will revise this internal file reader for VIIRS L1B files in a future SeaDAS release. This is a GUI only issue associated with Spectrum View and does not affect SeaDAS OCSSW processing.

Danny

byan0622 · by **byan0622** » Wed Jul 26, 2017 3:44 pm America/New_York

Thanks. Look forward to new version of SeaDAS release with this function.

by **OB.DAAC - SeanBailey** » Thu Jul 27, 2017 7:27 am America/New_York

You can use the Band Properties option to set the spectral wavelength for the bands manually (right click on the band in the File Manager tab to select the Properties GUI).
Once you have set the wavelengths, the Spectrum View GUI will identify the data as capable of being displayed.

Regards,
Sean