Sentinel -1 serie analysis

Microwave Toolbox
#1

Good afternoon,

I have two interrogations about the “S1TBX Time-series analysis with Sentinel-1”.

I work actually 31 images S1 IW (Grd) for the year 2020 for agricultual monitoring in Brittany (France).

1- Is it correct to apply a multitemporal filter (boxcar 3*3) on the series which have been preprocess with output data in dB backscattering ?

2- Is it correct to extract (with stack average) the min, max, avg, std… of the serie with Db data or shall I work with linear Sigma0 ?

Thanks for your answer,
Regards

#2

The answer to both of your questions is no - you should do all calculations in linear scale. Min and max will be correct both ways but boxcar, avg and std will not…

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#3

Thanks a lot for your answer, I agree with that, filter or statistical synthesis with DB data generates no correct output data.

On the tutorial “S1TBX Time-series analysis with Sentinel-1” on the ESA website, multitemporal filter and multitemporal statistical analysis seem to be process on dB stack images, which necessitate may be to be update.

Regards,

#4

I was the author of this tutorial and fully agree that it would have been more correct to perform the conversion at the end of the processing (filtering, resampling, averaging). I mostly did this from a didactical perspective because it allowed to perform the preprocessing within one graph (Figure 4) and then focus on the analysis of the data. As the tutorial was already considerably long, I decided to move this step into the preprocessing, and included a note telling about this inaccuracy, as kind of a compromise:

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#5

Good afternoon ABraun,

Thanks for your reply, yours tutorials are highly relevant and hep me to build S1 thematic courses and develop original research approaches.

For for multitemporal analysis with S1, the conversion in dB still represents a big issue as generally we need them before the end of the process in order to understand changes…idem for the speckle filter problematic, for multitemporal statistics as average or Std, sometimes according to the application, it is sometimes preferable to work within filter process…

Regards,

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