I think we see two different problems. The ones perpendicular to the image border are caused by tiling and unwrapping faults. The black ones seem to have a different reason. Are they still present if you zoom in?
At which step did you geocode your image?
Hi!
This is the detailed process I did to get the unwrapped interferogram.
Black lines are there since the software was installed. I did not install the software, our HPC admin did. The lines are present even when I zoom in. But when I export the images to geotiff and open in Arcmap, black lines do not show up. So, I am guessing that black lines can be ignored.
I am really confused because I am using 11 images and have generated 10 pairs of interferograms. Out of these 10 pairs, 9 are fine, only 1 is giving trouble.
Thank you.for help!
yes, these are just a glitch from your graphic card.
Is it an option to re-process the one image pair which has stripes from scratch to see if they occur again? It was a temporary issue?
Hi!
I processed the image on a local computer instead of HPC and now the image looks way better. The process was exactly the same. So, I dont know what is wrong. Strange thing is that when I used Linux, the image was not good and when I used Windows, the image was good. Sharing both the images. Anyway, thank you for help!
thank you for reporting the solution. Still a bit strange what caused the error in the end.
Hi again!
Sorry to disturb you again, but I am having another problem. I need IW2 and IW3 for my research. I am unable to produce a single image because snaphu is unable to unwrap the big image (I tried everything in my capacity as per your first commend on my first message). So, I split the image and then processed IW2 and IW3 separately. However, when I merged them, the result is unsatisfactory. When I mosaic them, I can still see a line going through the mosaic boundary. Can you please tell me what is wrong with mosaicing? (Attaching mosaiced image.)
Thank you for help!
do you get an error message?
If you define the number of tiles in a way that the size of a single tile does not exceed 3000 pixels (rows and lines), it should proceed.
If you create small subsets of your entire image before unwrapping you will inevitably get jumps at the borders after merging/mosaicing. So I would try to unwrap the entire image as one raster.
Is it an option to multi-look to a lower resolution? As you are looking at a quite large region, the initial resolution of 5x20 (or 10x10) meters might no longer be ultimately necessary.
Hi!
I am unable to find a way to decrease the tile size. I don’t know where that can be changed in snaphu export. (Attached is the snapshot of snaphu export GUI) Can you please tell me how to reduce the tile size? Also, I have started the unwrapping using ‘Multilooking’. I will let you know the result.
Thank you!
more tiles mean smaller single tile sizes.
You increase the “Number of Tile Rows” and “Number of Tile Colums” so each of the tiles becomes accordingly smaller.
Let’s say your initial raster is 10.000 rows (pixels) high and 10.000 columns (pixels) wide.
If you apply 10 tile row and lines, each of the single tiles has 1000 rows/columns (pixels) left.
You don’t even need to export again. Simply delete all temporary files (the tile folder and files with cryptic names), open the snaphu.conf, change the NTILEROW and NTILECOL parameters and save the file. Then run snaphu again.
Make sure to include pixel overlap as well, 250 is a good value.
Hi!
Thank you for your help! I was able to unwrap the whole interferogram at last!
However, this has caused some other problems (Image attached). Upper image is the interferogram generated using multilooking and lower image is generated by increasing the tile number to 100X100. Both images seem to be having a problem. Also, the deformation values in both images are differing largely. I am confused of which image is better and how do I overcome the respective problem. Can you please help?
Thank you once again!
Hi, I want to know if with sentinel toolbox I can do Topographic profile for to contrast the measuremnet of two interferograms in months continuous.
You can use the profile tool to plot interferogram values along a digitized line.
can do you sayme how I can do it?
there is a tutorial on how you can use the profile plot tool: https://www.youtube.com/watch?v=_g0F-hq3xTs
hi, did you use sarmint? i want to do the unwrapping process using virtual machine and not the snaphu plugin on snap, but i cant find sarmint .do you know where can i download it?
Hello, I have the same process as you. After step 4, I got the following file.
image|690x182
Now,However, which file should I open in step 5? None of these files seem to open.
@SUN-Ravenclaw: The files we see are the ones which are exported by SNAP. Now you have to run snaphu to create UnwPhase_ifg_[…].snaphu**.img**
After this file was created by snaphu, you an run the import and select this hdr file.
yes, but it has to be properly installed and executed (explained by @oana_hogoiu here: Snaphu Unwrapping Plugin)
