TOPS Interferometry Tutorial´ , page 8

Dear all
I am working with IW mode, Level1,SLC with snap. I should have a graph builder here as you can see in ´TOPS Interferometry Tutorial´ , page 8, TOPS Coregistration consists of a graph that reads two products but I do not have it. I do not know why?
You can see a red error in the end of my picture.
My data are:

is your study area located above 60° Northern or below 60° Southern latitude?
The error message indicates that there is no elevation information found online.

If your study area lies in the red area you should try to find another source of elevation data and use it in the ‘Back Geocoding’ step.

JAXA published a nearly global DEM with 30 meters based on stereoscopic PRISM data and it’s really good:

You can get it here for free after a short registration (see point 4):

Thank you. My study area is above 60 Northern. You are right but I do not know why I can not see this graph (I cut it from the ´TOPS Interferometry Tutorial´ , page 8 ) builder when I am using this :
Radar > Coregistration > S1 TOPS Coregistration > S1 TOPS Coregistration

you have selected the right module, in the tabs below there are the different parts of the graph, including ‘Back geocoding’
Maybe you will need to pull the window a bit wider to see it.

Thank you for caring but I pulled window but I did not see any thing.

I went to and I downloaded two zip file as my study area is Hailuoto iland, Finland. It has 2 parts in zip and I do not know how can I put both in External DEM part? Ithink I can put one of them, Am I right?
Should I put zip files?
These are files that I downloaded:

The GETASSE30 DEM is global and good enough for TOPS-coregistration.

It worked.:slight_smile:Thank you…mengdahl and ABraun

Dear Sir,

I have 3 images downloaded( around Charleston, SC ) to try TOPS Interferometry according to the tutorial:

(1) As showing in the tutorial only VV band is in the sample product( where can I download them? ), but in my products there are both VH and VV bands. Which makes the file is very large and SNAP exits exceptionally. So in SNAP I delete all VH related data, yet want to know any potential accuracy problem in processing?

(2) When I try to reduce the size of data by selecting a subset to process, it says some bands need to be re-sampled because their size is not same. When doing resampling, SNAP exits exceptionally( may be size is too large ). Any other method to select a subset( not across the boundary of IWs )?

(3) When doing coregistering data, the tutorial says SNAP can stack 2 or more images. Yet in the tabs of ‘TOPSAR Coregistering’ window are only 2 product names can be entered in tabs. How to add more images for coregistering?

(4) Just as ‘marjanmarbouti’ said before, there is no graph showing in the "TOPSAR Coregistering’ window( may be not for MacBook? ). I think this graph just tells what the processing will be for 2 images, but I concern what ‘back-geocoding’ means here. As ‘ABraun’ told me for another question, geocoding should be the last step in processing.

(5) It says on ‘Apply-Orbit-File’ tab that Orbit State Vectors ‘Sentinel Precise’ will be ‘(Auto Download)’. But there is also a red error message on the tab saying 'No valid orbit file found for 01-JAN-2000 00:)):)).000000…". If I check the box of ‘Do not fail if new orbit file is not found’, the results are blank images. It says orbit files may be downloaded from ‘’ and I find a lot of files there, by what parameter I can select the right orbit file for my product?

Thank you for the help!