# Generation of coherance and amplitude for flood mapping

respected all,
my study area lies in two subswaths IW2 and IW3 i want to generate coherence and amplitude for flood mapping. can anyone help me with the processing steps.
should i first merge the subswaths of pre event date and merge the subswath of post event date and then calculate coherance and amplitude ???
please help

Did you see my answer in here?

It refers to the same issue you raised yesterday, so why is a new topic needed?

sorry sir but this didnt worked i made the graph as suggested by you . also i want to compute coherence and amplitude for 7 months so how to get coherance of whole stack of images

Then please report so in the topic. If people take the time to help you, it would be nice to get feedback on their suggestions.
Currently, you are wildly mixing questions and aims (coherence, amplitude, C2 matrix, interferogramâ€¦) so it is hard for us to understand what is the problem in your case. We cannot see what is going on on your side, therefore we need clear descriptions.
So, according to this forumâ€™s rules, please keep the questions short and clear, report what you did and why it did not work, use screenshots, and only ask one question at a time. Otherwise we cannot provide help.

This is summarized here: FAQ - STEP Forum

The graph I showed was just for illustration of the order of the steps, you can still process them manually one after the other. So you can keep track of the intermediate results.

Especially when errors occur, graphs are not the best choice because we only see the final output.
So just split, coregister and create coherence, then finally merge the sub-swaths.

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okay sir im sorry got panicked . i will keep your instruction in mind .
regards vaibhav
so for now im using this approach will you please look at this and help

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Looks fine
If the result is empty, please conduct the steps manually outside the graph.

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i am able to get coherence for two diffrent subswaths . but after merging them nothing is coming

I have moved this to the existing topic.

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when i am merging the coherance of two different swaths using merge operator its giving me nothing please help

also if i want to clip this part out of iterferogram using vector shape file how it can be done in snap

I am not sure, but you could stop the graph after TOPS Deburst for a test (include topographic phase removal directly at the bottom of the interferogram operator) and wrtite the two sub-swaths without multi-looking and filtering. Please try to apply TOPS merge on the non-multi-looked sub-swaths first.

On your other question: Subset with shapefile not exact polygon shape

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thank you so much for your help sir what you told above it worked full area is coming
regards
vaibhav

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looks good!

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