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bopen / sarsen

Algorithms and utilities for Synthetic Aperture Radar (SAR) sensors
Apache License 2.0
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Use gamma-0 backscatter convention for RTC output #39

Closed maawoo closed 1 year ago

maawoo commented 2 years ago

Hi all, I was wondering why you chose to stick to the beta-0 backscatter convention instead of gamma-0 for the RTC output? Isn't the entire point of applying David Small's RTC algorithm [1] to get a terrain-flattened, gamma-0 normalized backscatter product? Furthermore, you might have heard of the CEOS CARD4L Normalised Radar Backscatter specification [2], which also endorses the gamma-0 backscatter convention.

Great software and I'm looking forward to hearing from you!

[1] https://doi.org/10.1109/tgrs.2011.2120616 [2] https://ceos.org/ard/files/PFS/NRB/v5.5/CARD4L-PFS_NRB_v5.5.pdf

alexamici commented 2 years ago

@maawoo I must admit I don't understand what you mean with:

beta-0 backscatter convention

Do you refer only to the attributes (that I agree are wrong, we forgot about them)? Or do you mean that the values need to have a different normalisation?

maawoo commented 2 years ago

Hi @alexamici, thanks for your quick reply! Table 1 in Small (2011) gives a good overview of backscatter normalization conventions and how they're calculated: Small2011_table1

So you're indicating that the values of output rasters created with sarsen rtc are correctly normalized to gamma nought, while their attributes wrongly refer to beta nought?