Dear @ABraun
Sorry for so many questions 
I applied:
Radar…interferometric……products….interferogram formation
Over ‘xml’ file for 26th April (imagine only vv band) and my interferogram is in figure1.
But when I applied exactly same process over another day-28th January- then I got below figure (figure2).
Why I have these right strips in figure2 (I did completely same process) ?
Thanks in advance.
very strange indeed. Are the two images of the bistatic product of 28.01. well coregistered? Make an RGB composite again to see if they match.
My guess is that SNAP doesn’t correctly overlay these images (even if they are from the same acquisition product)
I did not do coregistration. I used ‘XML’ file that is already coregistrated and then applied ‘interferogram formation’. How can i make an RGB composite?
Dear @ABraun
I have ‘bistatic’ and ‘pursuitmonostatic’ in my data. Interferograms are OK for bistatic mode but I get some strips over ‘pursuitmonostatic’.
Is there any way to remove them?
By coregistration I meant that both images should be already aligned when opening a TDX pair.
Right click on the original data opened by the XML > create RGB
select both intensity layers for red and green. The result shows you both overlayed as colors. Described here:
How large is the perpendicular baseline for both dates?
The pursuit mode is experimental and might not be comparable with the bistatic mode products.
I guess you distinctively applied for these data? Or was it an order from the archive?
Dear @ABraun
28th January: **
** Effective Baseline : 83.71583303770433 **
** Along Track Baseline : 78638.67863584885
26th April:
Effective Baseline : 566.217242676967 **
** Along Track Baseline : -110.4456833786547
I got data from my supervisor.
Do you mean it is not possible to remove stripes from mono mode?
28th January: **
** Effective Baseline : 83.71583303770433 **
** Along Track Baseline : 78638.67863584885
Possibly, the pursuit mode is not suitable
@mengdahl, any comments on this?
@marjanmarbouti can you make a red-green composite with only vv bands of a date?
Dear @ABraun
As i told you I want to see topography changes between two days (18 and 29) by TanDEM-X products.
As i know i should do below steps;
Step 1: Construct 2 interferograms
Step 2: Create DEM from each of the interferograms
Step 3: Calibrate DEM
Step 4: Subtract DEMs
But would you please let me know how can make DEM from from each interferogram? Is there any totourial for it?
I think I should do these steps that you already mentioned 
Create one interferogram per date (based on only one polarization), unwrap it and convert it to elevation. Then you can subtrackt the absolut elevations of both dates to search for changes.
exactly 
Dear @ABraun
Based on our discussion,I unwrapped interferogram in VV mode for 18th May (figure1) and then tried to convert it to elevation:
Figure 1.
Radar----interferometric----product-----phase to elevation
And as my area is over Alaska, then I chose ‘ASTER 1sec GDEM’ (Figure 2) but when I applied it, my result is completely black (figure 3).
Why?
Hard to judge by looking at the black image…
Some thoughts on this:
Nobody knows this data better than you. Be confident to seach for possible error sources, try to find explanations. In case you did, tell us what you already tried, so we can narrow it down. The “Phase to elevation” has no paramters to adjust so it must have another cause.
Dear @ABraun
Hard to judge by looking at the black image…
Some thoughts on this:
Is it really black or does it just have few extreme pixel values which distort the contrast?
I think it is extremely black.
Use the statistics tool to find out or set manual min/max values in the color manipulation.
Look at figure 1.
Try a diffent DEM, for example and see if it persists, even if the DEM is of very low resolution. You could at least exclude the ASTER GDEM as an erros source then.
I used ‘ACE 30 (Auto download)’ and the result is in figure 2.
Figure 2.
I do not know my elevation result is correct or not? And why ‘ASTER GDEM’ did not work?
Right-click on the data and select “Add elevation band” to get an idea of the DEM quality in your image…
I added two elevation bands for ‘‘ACE 30 (Auto download)’ and ’ ASTER GDEM’. I can not see any image in ’ ASTER GDEM’ but there is something in ‘‘ACE 30 (Auto download)’ (figure3). Why is like this?
If nothing helps, repeat the unwrapping with different parameters (e.g. SMOOTH instead of TOPO, there are lots of discussions on snaphu in this forum)
and so on, and so on…
Nobody knows this data better than you. Be confident to seach for possible error sources, try to find explanations. 
In case you did, tell us what you already tried, so we can narrow it down. The “Phase to elevation” has no paramters to adjust so it must have another cause.
Thanks. OK:slightly_smiling_face:
is some data below the sea level or generally near the coast?
Some DEMs only feature land areas.
If you are insecure about the quality, you can subtract the downloaded DEM from the result and create a difference image in the band maths.
What do you mean by data? There is some ridges near coast that I try to detect.
I mean that parts of your study area might lay within areas which are not contained in a DEM because they are off the coast, which could be an explanation for why the ASTER GEDM failed.
There is a small part of land in my images and most of my area is ice. Can this be a reason? If yes, then why it worked with
‘‘ACE 30 (Auto download)’?
as I said - some DEMs are 0 over water areas (or ice) and some are NoData.
No data - no reference height - no result
