DEM generation

Alright, will try that and let you know then, thanks :slight_smile:

Hi ABraun, this is how it looks like:

is this the case after the debursting?
Did you then have a look at the unwrapped phase?
Did you chose TOPO for the SNAPHU export?

@ABraun yes, that is after debursting. I chose TOPO and MCF for export.
The unwrapped phase (right after unwrapping) looks like a nice painting :mask::

@falahfakhri I tried to do all the process without subsetting but run out of memory twice (8GB RAM is not much). Is there a problem in subsetting the image?

Hi Ailin,

You can’t generate a normal DEM, when you have low values of Bperp (slide 13 from – 66.39 m). In fact, the document InSAR_Tutorial_ERS-Etna presents only the order of the steps! But the scene is like there (1 day in example) to get a DEM is not used for the case Sentinel-1! Bperp should be as large as possible. Usually to build a DEM choose scenes obtained with a low Btemp and perhaps a large Bperp.

For example, on page 132 ( ):
“Assuming we have more than about 20 repeat-pass SAR images, we can generate a stack of N coregistered multitemporal interferograms. Because our goal is to generate a new DEM or update an existing low-resolution or low-accuracy DEM, interferograms with short time separations and large baselines are preferred. This is critical to derive a high-accuracy DEM.”

So, to correctly build a DEM, you should have a lot of different scenes. And already from it it is necessary to choose a pair that best meets the criterion of building DEM.

Best regards,


thanks for the input, Igor. Multi-temporal data can surely increase the quality if interferometric analyses.

I was trying to do exactly what you describe but I am no longer sure if this is possible in SNAP:

Based on the publication provided by mengdahl here, interferograms should be combined after unwrapping:

Does anyone have an idea how they could be co-registered in SNAP?

@Ailin you can try 2 higher order consecutive Goldstein filtering but with lower values typically in logarithmic scale to ensure smoothing the results as much as possible while keeping fine details but with 8 GB of RAM & large scene it would be kind of difficult also I’m not so sure if this work in stbx1 but give it a try …

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@ABraun I’m digging a similar subject this days about averaging stacks …I would say it’s possible on paper to implement it on snap as separate enhancement but it’s not easy as it sounds.

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the main idea of subset is to reduce the scene size, in case of S1-A/B, the better is to split and choose only the bursts of your study area, still the question is raised about the coherence of your study area, take a look at this

The quality of your dem is strongly affected by coherence and atmospheric disturbances.

Take a look at this

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Thanks to all for your replies.

You are right Igor, I read that the optimum Bperp should be between 150 and 300 m (mine is 24m)
So I think it is not possible to build a DEM with Sentinel images. :worried: Also, the area of my work is mountainous and with low coherence values in some parts. And SNAP does not allow to work with different subswaths (eg: IW1 and IW3) so I can not combine Sentinel 1 and 2 images…

@aminevsaziz I used consecutive Goldstein filters with a subsetted part of the image but had the same results as the image I posted.

Yes, I used one burst.

So, should I try doing interferograms averaging, or is it worthless?

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Would you please to try out the whole image if that possible following the same processing chains, and let see what is the results? In this case there is no need to subset

Yes Falah, I will, although I tried and run out of memory but will try again
Let you know then, thanks

Hello,do you solve this problem?

I have done phase unwrapping successfully in order to create dem generation. The phase to height conversion is not working. There is another option called phase to elevation conversion.
Which process will i prefer for DEM generation?

and I am using TANDEM-X interferometry pair data. Is anybody has made DEM in SNAP?


hi, as i understand, you should use “phase to elevation” operator.

Please take a look at this topic answers your question.

Hi @ABraun
i made a DEM in SNAP and convert it to GeoTIFF format . i intend to use this file in ArcMap. based on fig below, how to remove black borders (No data value) from this DEM?

Thanks you :slight_smile:

you can define a NoData value in ArcMap directly in the symbology tab. Check the box and all 0 values become transparent.

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Thanks for quick responding. i did this earlier, but it didn’t work for me. i also tried with the procedure that is mentioned in fallowing website:
but it didn’t work too.

What value is the black area in your raster?