I'm running l2gen in Seadas 7.5.3 to process Sentinel-2 images. I want to use the NIR/SWIR method as I'm working in shallow waters and for the default AC option I retrieved weird Rrs values (either negatives or higher than 1) even for the band at 665nm.
This is how my command line looks like:
l2gen ifile=/home/laura/Desktop/Glenan/Glenan2019/S2B_MSIL1C_20190709T112119_N0208_R037_T30TVT_20190709T131959.SAFE/manifest.safe ofile=/home/laura/Desktop/Glenan/Glenan2019/Seadas/20190709bis.nc l2prod='Rrs rhos' brdf_opt=0 aer_opt=-9 aer_swir_short=1613 aer_swir_long=2200 aer_wave_short=740 aer_wave_long=865 cirrus_opt=false cloud_thresh=0.018 cloud_wave=2130.0 maskhilt=0
I'm using center wavelengths detailed in Pahlevan et al 2017 (Sentinel-2 MultiSpectral Instrument (MSI) data processing for aquatic science applications: Demonstrations and validations). However, I get this error:
Processing scan # 0 (1 of 5490) after 32 seconds
Aerosol selection bands 739 and 864
Aerosol selection bands 1613 and 2200 not available for this sensor
There is a problem in my command line? or NIR/SWIR correction is not available for MSIS2?
Also, in an old post from last year it says that it's not possible to obtain 10m resolution pixel from seadas (https://oceancolor.gsfc.nasa.gov/forum/oceancolor/topic_show.pl?pid=40047;hl=sentinel%2010m) but all the bands are resampled to 20m. I wonder if something changed in new releases of Seadas.
The MSI instruments on S2A and S2B have *slightly* different nominal band centers (see below). If processing S2B, you'll need to use 1611 and 2184 for the swir channels.
Also keep in mind that Nima provided vicarious gain coefficients for S2A, but for S2B we're still using gains of unity (so effectively no vicarious calibration).
This may also be impacting your retrievals.
Lambda(1) = 443 442
Lambda(2) = 492 492
Lambda(3) = 560 559
Lambda(4) = 665 665
Lambda(5) = 704 704
Lambda(6) = 740 739
Lambda(7) = 783 780
Lambda(8) = 835 835
Lambda(9) = 865 864
Lambda(10) = 945 943
Lambda(11) = 1613 1611
Lambda(12) = 2200 2184
The l2gen program still only outputs 20m resolution data from MSI. This will not change.
thanks a lot... I'll try with these wavelengths
about gains, I found some values for both Sentinel-2 satellite in the table 1 of this new Nima's paper:
Pahlevan, N., Chittimalli, S.K., Balasubramanian S.V., Vellucci, V. (2019) Sentinel-2/Landsat-8 product consistency and implications for monitoring aquatic systems. Remote Sensing of Environment 220, 19–29. https://doi.org/10.1016/j.rse.2018.10.027
are you change the band and are they work for aer_opt=-9? my question is after l2gen, i could not find the Rrs at any band during aer_opt=-1? are you successful on aer_opt=-9?