The Order of DEM Creating Steps

please friends how can i solve this problem in dem

this is natural data
i have big differences

Can you post a screenshot of the coherence image?

that is it >> i have mini project about this one please help me

i did subset to the image after Interferogram … that is right or no

you need better coherence for interferometry. Only areas with high coherence can be used later.

Please have a look at these answers:


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S1A_IW_GRDH_1SDV_20170407T115610_20170407T115635_016038_01A770_709D


getting interferometric DEMs in tropical areas is nearly impossible with C-band data because it is scattered ad the canopy and coherence is lost after a few seconds. Even with bistatic data (e.g. TanDEM-X) this is a challenge. So getting a DSM of the canopy is also not possible.

Unless you have P-band data (wavelenghs of ~74 cm) these canopies are not penetratable.

When are the exact dates of your two images?

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thank you very much for your answer

the number of GCPs for the coregistration is not possible in slc product

this is the date >>>>

no need the dem for all the area i have shown only for this area

that low vegetation as you see…

as stated, you should use the S1 TOPS coregistration instead of splitting the bands before.

Don’t apply Orbit Files or split the bands manually. This is all combined in the Sentinel-1 TOPS Coregistration. Use the SLC zip files as inputs and let the module to the rest.

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i know but My laptop is advance but this process took long time to finish in this step S1 TOPS coregistration … so… when can i do subset to my specific study area that i need …

second Q can i extract the dem for this area …

and how can i increase the GCP by S1 TOPS coregistration …

you can actually define the same subset within this module at the first step after the import. You just choose the subset under TOPSAR-Split by selecting the subswath (IW1/2/3) and the corresponding bursts (by dragging the grey bar towards the middle)

You cannot choose the number of GCPs here but it works good for interferometric purposes. (otherwise you can use the one with additional ESD from the same menu)

Can’t tell if the region is suitable for DEM generation, you’ll have to try.

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I guess this one I asked got lost in between. :slight_smile:

Another thing I had trouble is selecting of bursts. I tried to do it in both TOPS Coregistration and TOPS Split itself, but couldn’t manage it.

sorry, I overread that. Does this error come up in QGIS? I didn’t try the posted tutorial myself.

What was the problem in selection of bursts? You can limit the number of bursts by dragging the triangles towards the middle.

Yes it did come up in QGIS.

I thought I was supposed to select the bursts where I select subswaths. But I couldn’t find the section about dragging the triangles towards the middle. Where do I do it?

Like my example, your image looks like very low coherence due to vegetation I would assume from your optical image above.

In my case the two images were both from Sentinel 1-B with a 12 day interval between them. I believe in some areas you can get a 4 day interval using both S1A and S1B. Perhaps it would be good to test a vegetated area with the shorter interval to see how much it will improve results.

Based on https://sentinels.copernicus.eu/web/sentinel/missions/sentinel-1/observation-scenario, Europe would be a good place to test.

@musicnerd: Change it from this

to this

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