an empty product means that the coregistration failed.
Can you please check if both input products contain valid data before BackGeocoding?
First, how can I check that?
Second, I am goint to show that both files show the data until orbit file step.
Both images in orbit file are ok.
I don’t know another way to check valid data, can you teach me?
I changed the order of corregistration, I changed master image and slave image, curiously when I apply Back geocoding with SRTM 1Sec curiously always slave image doesnt show the data, but that slave image was the master image in another process that I did, and when that image was master the data was shown, so the problem is with slave image data in the Back Geocoding.
you can create a RGB image after BackGeocoding, please have a look at page 8-9 in this tutorial: Sentinel-1 TOPS interferometry
It didn’t work, red+green for master image, and blue for slave image, but it failled.
If your want to use SRTM 3Sec before the next update, please check the work around here: Gpt sentinel-1 back-geocoding error
I have found this link, http://skywatch-auxdata.s3-us-west-2.amazonaws.com/dem/SRTM90/tiff/ I have downloaded it, but I don’t know if I open it in snap, I don’t know how, it could solve my problem?
The address I have sent you is to make sure that the SRTM 3Sec data is correctly downloaded, because this has changed recently. So you don’t access the page to download it yourself.
As described here, you go to your snap installation directory and find the file called “snap.auxdata.properties” inside the ect folder
Open this file with a text editor and go to line
and replace it by
Save the file and close it. Next time SNAP searches for SRTM 3Sec data, it will access this source instead of the old one. The BackGeocoding step should then work again.
This will be fixed with the next update, but if you want to have SRTM 3Sec data automatically downloaded before you can change it yourself as described above.
Another thing is to make sure that SNAP is generally allowed to access online resources. Please make sure that port 443 is open in your firewall settings. How to Open a Port on Windows Firewall
Windows and Mac: How to open ports in your firewall
I’d like to know why with SRTM 1Sec slave image data is empty.
if it fails with both SRTMs it might really be the firewall.
I followed firewall steps, and the problem persists. I think that I have to wait the updates for SRTM 3Sec, for windows 10.
instead of auto download, you can also manually download a DEM and use it as an external DEM in this step
How can I import an external DEM in snap for windows 10?
Please use the search function of this forum:
- External DEM for SLC data coregistration
- How to import an external DEM into SNAP?
- Using External DEM 10x10m
- External DEM in offline mode
Can I use GMTED2010 DEM?. I am going to reproject it in WGS84 coordinates system.
yes, as long as it entirely covers your data and you store it as GeoTiff (in WGS84) you can use any elevation data as external DEM.
Ok, I am going to check the results, I hope this works.
Edit:
This is the file:
When I use external DEM this appears
And the process stops.
I used this another file:
The loading process worked. I am going to check if slave image data appears.
The rseult is the same, slave image didnt appear
I dont know what to do now, I changed dem and it didnt work.
Can I ask you a favor, I dont know if it is possible but I would like that you can make the same process with same pair to know if the problem is my computer, the images or the software.
In the case if you can do that these are the images:
S1A_IW_SLC__1SDV_20191212T105226_20191212T105253_030314_03779B_9982.zip
S1A_IW_SLC__1SDV_20191224T105225_20191224T105252_030489_037DA8_6D12.zip
For both images I made top-split: The split is IW3 Burst 4.
Are in south of Colombia and North of Ecuador.
Thank you.
I tetsted with your data. I applied TOPS Split (IW3, Burst 4), applied the orbit files, then BackGeocoding using SRTM 1Sec HGT (AutoDownload). I created an RGB image with the first (red and green) and second image (blue) and everything works fine.
I’m starting to believe that the DEM is not the problem in your case. Are you using the latest version of SNAP?
Thanks to show your results.
I am going to tell what I did after step by step.
1- I have the latest version of SNAP, version 8.0
2- I used another computer, and the problem persited in that computer.
3- I wanted to know if the problem were the software or the images, so I made a corregistration of other images of a different place (center of Colombia) and the Back Geocoding with SRTM 3Sec loaded very good (in the case of the images of the south of Colombia that I have showed you, the loading screen blocks), and the data of those other images appeared. But, I wanted to try with SRTM 1Sec for those images, the loading screen worked, but the slave image data didn’t appear, like in the case of the images of south of Colombia.
So these are my conclusions:
SRTM 3Sec worked for images of center of Colombia, and show all the data, master and slave image.
SRTM 3Sec dind’t load for images of south of Colombia, the problem is that I need those images for my study.
SRTM 1Sec loading screen works for images of south and center of Colombia, but the slave image data doesn’t appear for both cases.
So, the problem is related to the images of south of Colombia, but it worked for you, so I don’t know what could be the problem, I have tried everything, changing dem, changing computers, changing images, so I don’t know what to do.