I don’t know. Currently, S1TBX is in between two contracts and it is not yet clear when the next contract will start.
thanks for the clarification
A number of help pages do have the citation to the reference papers. We’ll add them for the speckle filters.
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Sometimes, there is a kind of reference in the text but no info to have the title, authors, and so on
For example, in Integer Interferogram Combination :
It is possible to stack several interferograms of the same site to increase their clarity or reduce the number of fringes, thus creating an integer interferogram combination (IIC) [R13]. The combined interferogram can have a better altitude of ambiguity ha than any of the source interferograms.
How do I access to R13 ? I tried the search field but the only result is the Integer Interferogram Combination its self
Thanks in advance
The “Lee Sigma” filter for filtering intensity data implements the “improved Lee sigma filter” algorithm given by [1].
The “improved Lee Sigma” filter for filtering polarimetric data implements the “extended Lee sigma filter” given by [2].
[1] Lee J S, Wen J H, Ainsworth T L, et al. Improved Sigma filter for speckle filtering of SAR imagery. IEEE Transactions on Geoscience Remote Sensing 2009; 47(1): 202-213.
[2] Lee, J. S., Ainsworth , T. L., Wang, Y. & Chen, K. S. 2015. Polarimetric SAR Speckle Filtering and the Extended Sigma Filter. IEEE Transactions on Geoscience and Remote Sensing, 53, 1150-1160.
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Which are some non-linear filters which can be used for speckle filtering of S1 GRD data?
Would it be possible to add the Enhanced Lee (https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=62623) and Enhanced Frost on future releases or updates? It would be very useful for ocean applications and so far, no toolbox has it. There was a distribution of pyradar (https://pyradar-tools.readthedocs.io/en/latest/tutorial.html) but got lost in time. Thanks 
One more question regarding references…
I would like to learn more what’s behind Speckle Filtering -> Single Product Speckle Filtering -> Refined Lee
As there are more than one “Lee” filters (btw Refined Lee is also in Polarimetric Filtering - is it the same algorithm? Looking at github not necessary) and in various articles “Refined Lee” is referenced to different publications, I’m quite lost.
SNAP Help in “Speckle Filter” chapter gives information on four sources of information. I assume information regarding Refined Lee speckle is in J. S. Lee, E. Pottier (2009) “Polarimetric Radar Imaging from basics to applications” to which I do not have access. But according to the book contents which I’ve found it’s 150-152 page. Maybe someone of you has it and could check the references there?..
Also, while looking at github I’ve noticed that the size of the window in this Single Product Refine Lee Filter is blocked to 7x7. Could you please explain me why?
The link to the github.
(I am not good at reading scripts so I simply cannot find the link between the script and any scientific publication, that’s why the question above…)
The algorithm for Speckle Filtering -> Single Product Speckle Filtering -> Refined Lee is the one given in Lee’s book (J. S. Lee, E. Pottier (2009) “Polarimetric Radar Imaging from basics to applications”). The 7x7 window is used for edge detection. Details can be found on page 150-152 in Chapter 5 in Lee’s book.
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Hi!
An update in the Filters description in SNAP would be very useful. It is not very clear still after which reference the filters are implemented. For example, I am finding that a direct python implementation of the Lee filter is giving significantly different results compared to the same image processed in SNAP using the Lee filter. I am using the original Lee.J.S, 1980, Digital Image Enhancement and Noise Filtering by Use of Local Statistics, IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol. PAMI-2, No.2 implementation. However, looking at the code in github, it seems the rationale doesn’t follow the same line there. Could you provide a good reference for all the filters implemented in SNAP? Is important for people that are doing speckle filtering to know exactly what they are using.
Thank you!
Thank you for the reference to Speckle Filtering -> Single Product Speckle Filtering -> Refined Lee. Can you tell me if this is the same reference to Polarimetric–> Speckle Filter–> Refined Lee (SNAP v7)? Or is the reference later in Lee & Pottier’s book, “5.4.2 Refined Lee PolSAR Speckle Filter” pp 161-165?
For single product Refined Lee and polarimetric Refined Lee, the references should be respectively “5.2 Filtering of Single Polarization SAR Data” and “5.4 Polarimetric SAR Speckle Filtering” in Lee & Pottier’s book
I understand that the speckle effect appears in SAR images, but I wanted to know whether is it exclusive to SAR images only, or does occur in images created by passive sensors or by RAR satellites ? If only SAR images show speckles, why?
It is exclusive to coherent sources, so for example lasers produce speckle too. It is signal, not noise.
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Could you please elaborate what you mean by that?
I am so confused when some literature as (Lee 1994) mentioned that speckles were granular noise resulted from interference. and (Engdahl, 2013) said it’s “noise-like” appearance.
Also, how come single light source cause such effect, is it because of interference emerged from diffraction?
Well, whether it is “noise” is practise depends on the application - in intensity-based applications it is usually a nuisance. It is “noise-like” in the sense that it is random but fully reproducible if coherence has been preserved.
It can be viewed as the end-result of the coherent summation of reflections from many “elementary scatterers” that are much smaller than the resolution-cell.
So, can the doppler shift contradict the frequency coherence that causes speckle effect? As if the observed frequency of echoes change between multiple scatterers, so the signals won’t completely interfere and speckle won’t appear?
I’m not sure if I understand your question but speckle is present in fully focused images where the doppler-history difference has been used to focus the image. And in any case the elemental scatterers are much smaller than the resolution-cell and cannot be resolved.