How to get the rhos_478 in Seadas?

[jialin699]

Hello，
I used Seadas_8.0.0 gui in linux to process L7 ETM date.Now I have trouble running l2gen. I want to obtain rhos_478 value.But there are many NaN in rhos_478 of the L2 Products.
Any thoughts or suggestions would be very helpful!
Thanks,

Jialin699

[OB SeaDAS - xuanyang02]

It’s a calibration issue. We don’t have gains for L7 (so unity values are used). As a result, this scene has negative rhos. We do not provide the calibration adjustments that would be necessary to get valid retrievals, but you can see if this paper helps: https://doi.org/10.3390/rs10091337

Attached is rhos_478 from the L2 scene generated from LE07_L1TP_131042_20020106_20170201_01_T1

Screen Shot 2021-12-15 at 11.44.12 AM.png (300.71 KiB) Not viewed yet

1) You can remove Valid-Pixel expression -- in the File Manager panel, right clicking rhos_478 and choosing Properties will pop out the Properties window that allows you to edit the properties including Valid-Pixel expression

Screen Shot 2021-12-15 at 11.49.54 AM.png (127.93 KiB) Not viewed yet

2) In the color manipulation panel, you can choose "From Data" for the Range. The max is -0.04, it seems that too much Rayleigh is subtracted which means gains need to be higher than 1

Screen Shot 2021-12-15 at 11.52.21 AM.png (166.63 KiB) Not viewed yet

[jialin699]

Thank you Very much!!
I got it!
But I have an another question, Rrs is remote sensing reflectance, while rhos is Rayleigh (and gas)-corrected "surface" reflectance. I read some material:
rhos = pi*(Lt-Lr)/Ed where Lt is total TOA, and Lr is rayleigh, and Ed is the usual F0 * cos theta * etc.
Rrs is effectively Lw/Ed.
It almost looks like the rhos≈π*Rrs

However, in this study area, the relationship between Rrs and rhos varies greatly (2-125) based on Landsat 7 images, It makes me confused.
I have some in-suit Rrs data, how can I build the relationship between Rrs and rhos?