How to use TerraSAR data to creat DEM?

can you show a histogram of your coherence?

What is the temporal and perpendicular baseline?

I open view> toolbars>tool windows>insar tool.

OK,I open the histogram of coherence.

thank you. Coherence is not that bad actually. Values larger 0.4 are good, but for some areas you should be able to retrieve elevations with this. I’m more concerned about the extreme ramping of the values in NNW-SSE direction. Can you make a profile along this direction to maybe estimate the inclination of the whole gradient?

OK,but I’m afraid to ask another problems.:confused:You told me about retrieve elevation with this and make a profile along this direction to maybe estimate the inclination of the whole gradient.Could you told me more details steps or releveant ?Please forgive my request,there are many problems do not understand.:joy:Thanks!

Have a look in the SNAP internal help if you are insecure about different points. There is explained, point by point, how you make a profile for example.

Maybe you should also start a bit earlier with SAR basics before addressing InSAR topics or have a look at the numerous topics in here which are dealing with the same problems:

Thank your help.:blush:

Sorry, I open the file which isn’t downloaded from website yesterday night.:sweat: But I still thank you.

maybe some of these tutorials help you in general on how to deal with SAR data:

Input to Google Earth DEM elevation is relative elevation, right? How can I determine its absolute elevation,otherwise, how do I know the accuracy of the generated DEM.Thanks

did you perform Phase to Elevation?
Which steps were applied?

yes,I did perform phase to elevation>Range-Doppler Terrain correction,then export to geogle earth.

after Phase to Elevation you should be getting absolute heights.
The Google Export is not necessary, I would rather choose to include the DEM in the TC module as well by checking the respective box so you can compare your results to the SRTM data.

When I do terrain cottection step,show the dialog ,What is the role of “DEM” in the dialog box? Do i need to check it?

It will add a DEM-band, in your example SRTM 3sec (Auto download).

OK,Why are these two elevation values have such a big difference?Did I understand the wrong or the process is wrong?

you probably did nothing wrong but repeat pass interferometry (scenes from different dates) cannot produce high quality DEMs in most cases. How many days are your scenes apart?

Oh,this is the data I use.
TSX1_SAR__SSC______SM_S_SRA_20140610T225348_20140610T225356.xml TSX1_SAR__SSC______SM_S_SRA_20140702T225349_20140702T225357.xml

can you open both data sets and select Menu > Radar > Interferometric > InSAR Stack Overview
Add Opened > Overview

and post a screenshot of it?