Couldn't calculate interferogram and coherence

Dear all,

I try to calculate interferogram and coherence value based on Sentinel-1 imagery and nothing happens. I have only noise for interferogram and Nan for coherence. It happens even I use standart graph (Graphs-Radar-InSAR Graphs-Topsar Coreg Interferogram). I tryied to perform processing for different geographic areas and have the same result. Could someone please help me to understand what’s wrong with processing or PC? My PC is powerful (RAM about 62 Gb)…

I have same problem. I couldn’t find any phase difference in interferogram generation. How can i do ?

Please have a look at our updated tutorials. Instead of executing the graphs it is often better to compute the steps separately to keep track of the intermediate products and see where the error occurs at the first time.
Sentinel-1 TOPS interferometry

Based on the present information, we cannot tell what exactly the problem is.

it loooks like you are using images which are shifted along-track. It is important to reduce the number of bursts in both images (in the Split operator) to the joint area which is covered by both images. Only this overlapping area can be used to generate an interferogram.
More information is given here on page 8: DEM generation with Sentinel-1 - Workflow and challenges

Dear ABraun,

thank you for tutorials! I found the step when error appeared. During S-1 Back Geocoding processing slave image is disappeared. Master image is OK. I selected the same area with only 2 bursts for each image. It seems suitable for InSAR processing (screenshot is below). I use Aster GDEM because of SRTM doesn’t cover my study areas. Do you know why it could happens?


Good, we can work on this. An empy slave during the BackGeocoding means that the coregistration failed because not enough matches were found between the master and the slave.

The problem with ASTER is that it is not automatically downloaded. So no DEM was used in your case which probably caused the error. Try ACE30 or GETASSE30 for a test, they should be sufficient for the BackGeocoding. If you have selected more than one burst, the following step is Enhanced Spectral Diversity.

Thank a lot! It works! :slightly_smiling_face:

@ ABraun I followed workflow for DEM generation with sentinal-1 but i got GC runnuing error in Back geocoading processing step. What is the GC running error and how can i sloved this error?

This one? S1 IW slc: GC overhead error in back geocoding

It is related to your system’s memory. Did you reduce the number of bursts to a minimum as suggested?