Opening VIIRS L2 in SeaDAS

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kelseaedwing
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Joined: Mon Jul 12, 2021 4:43 pm America/New_York

Opening VIIRS L2 in SeaDAS

by kelseaedwing » Thu Jul 22, 2021 7:10 pm America/New_York

Hi,

I want to process a L1A VIIRS image to a L2. At first, I used the L1A to generate a GEO file and then used l2gen to produce a L2 image. However, the L2 image will not open in the SeaDAS 8.0.1 GUI.

I then tried something different and processed a VIIRS L1A image to L1B using calibrate_viirs. But when I tried creating a GEO file using the L1B, I get a JAVA error. I can create a L2 image using the L1B image (with no GEO file) but it again does not open.

Am I missing a step that is causing my L2 VIIRS image to not open in the SeaDAS GUI?

Thanks!

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OB SeaDAS - xuanyang02
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Re: Opening VIIRS L2 in SeaDAS

by OB SeaDAS - xuanyang02 » Fri Jul 23, 2021 10:57 am America/New_York

l2gen on VIIRS takes L1(L1A or L1B) + GEO. You can download VIIRS L1A and VIIRS GEO from https://oceandata.sci.gsfc.nasa.gov/VIIRS-JPSS1/L1/

geolocate_viirs takes VIIRS L1A and creates VIIRS GEO https://seadas.gsfc.nasa.gov/help-8.1.0 ... viirs.html
calibrate_viirs takes VIIRS L1A and VIIRS GEO and creates VIIRS L1B https://seadas.gsfc.nasa.gov/help-8.1.0 ... viirs.html

kelseaedwing
Posts: 17
Joined: Mon Jul 12, 2021 4:43 pm America/New_York

Re: Opening VIIRS L2 in SeaDAS

by kelseaedwing » Fri Jul 23, 2021 4:30 pm America/New_York

Got it, thanks! I think the GEO file I had created in SeaDAS was incomplete so the l2gen image was empty.

I do have another question. I am trying to compute an FAI using VIIRS and I was under the impression that Rrs values were needed. However, l2gen only produces Rrs for VIIRS bands up through the 667 nm band, but I need the 746 and 868 nm bands as well. Do I need to do something else to get these bands or does the FAI not require Rrs values?

OB SeaDAS - xuanyang02
Subject Matter Expert
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Posts: 172
Joined: Tue Feb 09, 2021 5:42 pm America/New_York
Answers: 1

Re: Opening VIIRS L2 in SeaDAS

by OB SeaDAS - xuanyang02 » Tue Jul 27, 2021 12:48 pm America/New_York

It is a bug that l2gen GUI does not allow you to choose Rrs_746 and Rrs_868, we'll try to fix it.

For the time being, here is a workaround by running l2gen on command line instead of GUI:

Click "Save Parameters" in the "Parfile" section on the l2gen GUI's "Main" tab, and save the Parfile as l2gen-tmpParFileRrs.par in the directory where you save your VIIRS files.

Use a text editor (vi or emacs) to open l2gen-tmpParFileRrs.par. Add a line in the file:
l2prod=Rrs_vvv chlor_a Rrs_746 Rrs_868. If theres is already a line "l2prod=Rrs_vvv". Add "Rrs_746 Rrs_868" to the line.

In a terminal, in the same directory, do "l2gen par=l2gen-tmpParFileRrs.par".

Here is a thread on a similar issue for your reference: viewtopic.php?f=7&t=2365&p=8373&hilit=p ... 57f2#p8373

BTW, you should start a new thread when you have a new question.

kelseaedwing
Posts: 17
Joined: Mon Jul 12, 2021 4:43 pm America/New_York

Re: Opening VIIRS L2 in SeaDAS

by kelseaedwing » Tue Aug 03, 2021 10:06 am America/New_York

Thanks for all the help OB SeaDAS - xuanyang02! I changed the saved parameters file and it worked. I'll make sure to start a new thread when I have a new question. Thanks again.

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