DEM generation

Microwave Toolbox
#41

Hello,
Is it possible to do an interferogram flattering using SNAP? how?
thank you

#42

And I have another problem
When I want to coregister the image of 2016 from this area software says that can’t download the orbit file
And offered to download it from a site and replace in a specific folder
I do it but, it doesn’t work yet!
I don’t know what shoud I do!
After replace the files, I should select what option to do it?!

#43

Dear all
please help me
when i want to use DEM generation option of SNAP it gives me an error

Capture.PNG546×554 54.7 KB

what shoud i do?
and why it show me this error?

#44

I try to make a graph for my purpose
like this:

Pasted image734×930 93.4 KB

is it wrong?
is there any problem about it?
when i want to run it, it says that,

I can’t understand why?
in stitch and unwrap tabs there is nothing to set!!
and I can’t find these 2 step separatly in software!, where are they?

#45

Don’t use those unwrap and stitch. Update to the latest SNAP version and use export to SNAPHU, use SNAPHU on linux and then import it back into SNAP.

#46

thank you but once i do it , as I said before I get bad result in transform phase to height
after that I try to use DEM generation option and get this error

I don’t know what should I do!

#47

can anybody help me?
what is the reference height for computing elevation from interfrogram?
please give me answer!

#48

Might be this helpful https://www.ims.tuwien.ac.at/publications/tuw-138083.pdf

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About InSAR atmospheric effects
#49

thanks a lot:smiley:

#50

Hi everybody
do you know , what is DEM accuracy created from Sentinel-1 data in S1TBX?
or how can we calculate it?

#51

You could compare against a validated DEM of higher quality. In general repeat-pass InSAR DEMs often have quite large errors due to loss of coherence and atmospheric artifacts.

#52

thank you mengdahl
can you explain more?
how should I do exactly?
I know that In general repeat-pass InSAR DEMs often have quite large errors due to loss of coherence and atmospheric artifacts but I do it at urban area and have high coherency!
do you think it has low accuracy?

#53

High coherence does not help if you cannot unwrap the phase, so it depends on the situation.

#54

I do unwrapping step without any problem

#55

You should study assessment of DEM quality, then compare against an existing high-quality DEM and let us know how well it works. I personally would like to know the asnwer! :slight_smile:

#56

Thank you so much mengdahl!
surely I report my result
can you give me a recommendation for reading about assessment of DEM quality?

#58

Can you please send me graph builder .xml file for DEM generation.
akshaygore@live.com
Akshay Gore

#59

@FTP Can you please send me graph builder .xml file for DEM generation.
akshaygore@live.com
Akshay Gore

#60

@Sara.Aparicio
Can you please send me graph builder .xml file for DEM generation.
akshaygore@live.com
Akshay Gore

#61

instead of using graphs, try to follow these steps and check if the output of each operator matches your needs.
Just applying a graph will probably end in bad results. Futhermore, the unwrapping can not be included in a SNAP graph and has to be performed externally.

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