Rayleigh correction

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osrani
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Joined: Mon Nov 19, 2018 10:11 am America/New_York

Rayleigh correction

by osrani » Tue Dec 18, 2018 10:31 pm America/New_York

Haii
I recently started working on seadas. I am processing MSI sentinel data .I have successfully processed sentinel-2 data using l2gen command with ifile and ofile.But I need only Rayleigh corrected image.In previous posts I found , we can get only rayleigh corrected images by rho_nnn.I think this should be an intermediate file created during processing of l2gen command.
I  am eager to learn the basic commands like
1.How to display our processed image by command
2.How to save images in our required formats like tiff,hdf or nc
3.How to retrieve only required parameters (like only rho_nnn)
Please guide to get some refernces to know these basic things

Regards
rani

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OB WebDev - norman
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Rayleigh correction

by OB WebDev - norman » Wed Dec 19, 2018 9:06 am America/New_York

Hi Rani,

I suggest you have a look at some of the introductory videos that the SeaDAS
folks put together to get you started.

https://seadas.gsfc.nasa.gov/tutorials/video_tutorials/

There is also a good collection of help pages available for the various SeaDAS
programs.

https://seadas.gsfc.nasa.gov/help/

Regards,
Norman

P.S.  I believe you are looking for rhos_nnn.

osrani
Posts: 19
Joined: Mon Nov 19, 2018 10:11 am America/New_York

Rayleigh correction

by osrani » Wed Dec 19, 2018 10:49 am America/New_York

Thank you norman.
Yes I want rho_nnn for  sentinel-2 image.
will this command will work for rhos_nnn
l2gen ifile="" ofile ="xxxx.L2" product=rhos_nnn

OB WebDev - norman
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Rayleigh correction

by OB WebDev - norman » Wed Dec 19, 2018 11:00 am America/New_York

Note the "s".

OB SeaDAS - dshea
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Rayleigh correction

by OB SeaDAS - dshea » Wed Dec 19, 2018 3:16 pm America/New_York

need to set "l2prod=rhos_nnn" not product.

run l2gen on the command line without any options to get a list of the options available.

osrani
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Rayleigh correction

by osrani » Thu Dec 20, 2018 5:45 am America/New_York

Thank you  so much .It  worked.
Now  I am this assuming  rhos_nnn are only rayleigh corrected .
I observed that F0 values below are not matching with F0 given in metadata.
Bnd   Lam       Fo    Tau_r     k_oz    k_no2    t_co2   awhite       aw      bbw
    0  442.000  187.338 2.366e-01 2.837e-03 5.072e-19 1.000e+00 0.000e+00 7.057e-03 2.187e-03
    1  492.000  196.024 1.563e-01 2.592e-02 2.844e-19 1.000e+00 0.000e+00 2.111e-02 1.410e-03
    2  559.000  182.410 9.115e-02 1.042e-01 8.920e-20 1.000e+00 0.000e+00 6.234e-02 8.149e-04
    3  665.000  151.348 4.489e-02 5.033e-02 8.658e-21 1.000e+00 0.000e+00 4.177e-01 3.945e-04
    4  704.000  142.593 3.559e-02 2.055e-02 3.752e-21 1.000e+00 0.000e+00 6.960e-01 3.112e-04
    5  739.000  129.029 2.919e-02 1.096e-02 1.494e-21 1.000e+00 0.000e+00 2.672e+00 2.542e-04
    6  780.000  117.556 2.353e-02 7.322e-03 4.277e-22 1.000e+00 0.000e+00 2.675e+00 2.038e-04
    7  835.000  104.151 1.851e-02 3.559e-03 1.882e-22 1.000e+00 0.000e+00 3.513e+00 1.577e-04
    8  864.000   95.478 1.554e-02 2.277e-03 3.049e-23 1.000e+00 0.000e+00 4.588e+00 1.335e-04
    9  943.000   81.782 1.092e-02 7.461e-04 9.177e-26 1.000e+00 0.000e+00 2.211e+01 9.309e-05
   10 1611.000   24.706 1.280e-03 0.000e+00 0.000e+00 1.000e+00 0.000e+00 7.557e+02 1.048e-05
   11 2184.000    8.775 3.800e-04 0.000e+00 0.000e+00 1.000e+00 0.000e+00 2.282e+03 3.043e-06

but in metadata the values are :
Band F0
442     1874
492     1959.77
559     1824.93
means F0 In metadata is 10 times greater than this F0 .
..... and band10 is 1376 with F0 365.41 is not included in the list..
I did not understood  these things .Please  clarify these things

OB.DAAC - SeanBailey
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Rayleigh correction

by OB.DAAC - SeanBailey » Thu Dec 20, 2018 8:14 am America/New_York

Units.  The factor of 10 is because one set is in  W/m^2/nm and the other mW/cm^2/um

The 1376nm band is the cirrus band, used to detect high cirrus clouds.  It is not included as part of the standard atmospheric correction processing because, well, we can't be certain how high the cirrus clouds are - so can't make a reasonable adjustment to remove the Rayleigh component.  There is a special output product for it, rho_cirrus - it is NOT Rayleigh corrected.

Sean

osrani
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Rayleigh correction

by osrani » Thu Dec 20, 2018 11:32 am America/New_York

Thank you sean
Is rho-cirrus can also be obtained as l2prod=rho-cirrus????
What is the importance of this product .

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Rayleigh correction

by OB.DAAC - SeanBailey » Thu Dec 20, 2018 12:00 pm America/New_York

It's rho_cirrus not rho-cirrus, and yes you would add it to the l2prod list.
If you're interested in screening based on cirrus cloud detection, it might be interesting to use this product.  We've not put much effort into exploiting it for ocean color processing.  The band was intended for the cloud/water vapor processing (so the MODIS Atmospheres team uses it...)

Sean

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