# Coherence from slaves from many date Back-Geocoding result

After Back-Geocoding a batch (8) of S1 images I would like to process coherence between slave pairs. My thinking is that all the slaves and master are precisely aligned, particularly after Enhanced-Spectral-Diversity, and I would like to calculate coherence between any pair, and not just the slaves relative to the master. This would provide coherence results that are all precisely aligned. Can this be done or is there another method to achieve similar results.

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Slave-slave interferogram formation. Following!

So you have 8 S1 images coregistered in one stack and you would like to calculate coherence between slaves? currently in SNAP if you calculate interferogram for the stack you will create a stack of interferograms and coherence between mst-slv1 mst-slv2 etcâ€¦
The tool that would be useful for you will be soon in SNAP 8 - it will be called â€śmultimasterâ€ť and this operator will create products pair slv1-slv2 slv2-slv3 etcâ€¦ for which you can calculate coherence

It is already implemented for coherence (not yet for interferograms)

Never used but it could be also done applying the coherence formula using python or matlab.

A pity that the Band math does not allow to do complex conjugate multiplicationsâ€¦ (if I am right)

This option currently produces an error, it is already reported and will be tackled within the further development of multi-master functionalities.

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Hi all. Is there any news on this topic?
I have created some interferograms with external software (python) by combining pairs of coregistered slaves, but I cannot compute the flat Earth and topographic terms for these slave-slave pairs, so they are not useful for me.

I created a new issue relative to multi-master coherence processing of multi satellite (S1A and S1B) stacks:
The issue is coherence pairs are computed pairwise through S1B dates, the last S1B and first S1A date, and then pairwise through S1A dates. So the only multi satellite pair is not useful since the longest time baseline. When computing multi-master the dates should be sorted and run pairwise. Currently coherence processing appears to run pairwise through a stack that is reverse sorted by satellite first, and then by date.