Re: NEGATIVE rhos_ (bit flag 3 value 8) for entire scene Sentinel-2 DSF
Posted: Wed Dec 06, 2023 4:11 pm
Hi Quinten,
Do you have any insight to the thought process you used in this particular case to transition from the 0.24 AOT estimate to the 0.12 AOT estimate and particularly why you knew to not go below the 0.12 value? I have a belief that the AOT estimate also impacts the offset parameter for our SDB products during the calibration step. Knowing when and why this AOT estimate changes aside from the obvious would be good to know.
Should I be experimenting with reducing the AOT estimates in targets that return a preponderance of negative reflectances when TOA reflectance is not lower than the computed Rayleigh? Or should more development occur first?
The reason I mentioned previously that negative reflectances were an issue was that we are using the 740 band as a surrogate for turbidity (additional scattering) in very shallow water. Additionally, the ~833 band is often used when computing NDWI-- a useful mask for some of our products. Furthermore, the 704 band can be used in masking aquatic vegetation (Sargassum) using NDVI.
-Bryan
Do you have any insight to the thought process you used in this particular case to transition from the 0.24 AOT estimate to the 0.12 AOT estimate and particularly why you knew to not go below the 0.12 value? I have a belief that the AOT estimate also impacts the offset parameter for our SDB products during the calibration step. Knowing when and why this AOT estimate changes aside from the obvious would be good to know.
Should I be experimenting with reducing the AOT estimates in targets that return a preponderance of negative reflectances when TOA reflectance is not lower than the computed Rayleigh? Or should more development occur first?
The reason I mentioned previously that negative reflectances were an issue was that we are using the 740 band as a surrogate for turbidity (additional scattering) in very shallow water. Additionally, the ~833 band is often used when computing NDWI-- a useful mask for some of our products. Furthermore, the 704 band can be used in masking aquatic vegetation (Sargassum) using NDVI.
-Bryan