I put unzipped folder there although that big unzipped folder has several zipped folders (figure3) but when I chose again ‘ASTER’ for converting unwrapped result to elevation, it did not work.
After you downloaded all required tiles, you can open them in a GIS, make a mosaic and use it as “External DEM” instead of selecting ASTER in the dropdown.
There was something wrong with zip folder of all data that earth data sent to me, now, I used the link and downloaded all and put in folder (figure 1). I think i should do something until ASTER dem can be active because I repeated processing and again it was failed.
I did not work with DEM result before, but in my idea, when I subtract the downloaded DEM (ACE30 DEM) _figure1_from the result (my created elevation) _figure2_and create a difference image in the band maths. If the DEM has high quality, the difference should be very little.
Am I right? If so, based on difference result between DEM and my elevation result, the difference is between (-3.32 to 18.35)figure3.
figure3
Or maybe, I should do some calibration first on my elevation result (for instance, subtract height value at a stable point like airport here and add 13 m (resulting in sea level reference))) and then compare my elevation result with ‘ACE30 DEM’?
load all ASTER files into SNAP and combine them into one large raster with the moasic tool.
Comparing your InSAR elevations to the ones from the DEMs is not a good idea because they wer created based on different data and methods. Additionally, if they have different spatial resolutions, they are not suitable for subtraction from your InSAR elevations.
But you need a DEM for proper terrain correction of your InSAR elevations and I would suggest to use ASTER.
There are some ways to do mosaicing in SNAP but as our data are not SAR products, I think we can only use mosaicing in SNAP.
I used below steps;
Raster…Geometric operation…mosaicing
Then I added all zip files and I chose UTM zone_parameter projection=4_ here (figure 1) and when I went to another step (variable and condition), then I got this error(figure2).
How can compare my elevation result with ‘ASTER DEM’. There is a option to adding band for ‘ASTER DEM’ but it is empty. Shall I subtracted the mosaic I made from my elevation result for checking quality?
You told me:
As a last step, you can apply Tange Dopper Terrain Correction so both elevations are projected into a coordinate reference system Then you can stack them and compare the elevations.
Shall I do it now?
I tried to do it (figure 1) but them my result is like this (figure2). I think something is missing in image.
Another thing that is weird for me is here;
Why when i applied terrain correction by using external file, the result is bigger that my elevation result. Please look at below;