the images above had a perpendicular baseline from 13 m, not enough - you are right.
The test below was made with an image pair of 12 days and 138 m, but results are still not very good. I wonder why it worked so well in the Turkey example from above and there are hardly usable results in Mali where conditions are even better.
You can only keep looking at interferograms and hoping to find a pair with the least amount of ionospheric/tropospheric disturbance. What is your use-case BTW? Isn’t SRTM good enough in that area?
Actually I’m just curious about the quality which can be achieved. We use the dem for runoff modeling and groundwater exploration. If some fractures could be enhanced I would be happy.
But I’ll keep testing.
Hi everyone! I have a pair o images with Bper=103,29m and model. Coherence=0,89. I have processed the pair and when it comes to the Histogram of Phase I get this:
I am trying to create a DEM of Nassiryia area. I know that the baseline is not ideal for realizing a DEM (i.e. 53.48), while the coherence is reported in the histogram:
As you can see, they are quite different, but the second one is the real aspect of the topography. Also, I have compared the second output (i.e. bands=“elevation”) with the elevation in Google Earth, but the two data are different. Could is it a problem caused by wrong baseline?
Moreover, I save the dem as GEOtiff, but when I open it on ArcGIS, this is the image:
I know that the “elevation” image is the right while the “elevation_VV” image is wrong. Can save only the “elevation” image as GEOtiff without the “elevation_VV”?
Thank for your reply and I hope I am not hijacking the thread here!
elevation_VV is the one genetated by Sentinel-1, the other is the DEM used for Terrain Correction. The first, although the quality is not perfect, is your result.
ALOS is L-band, Sentinel-1 is C-band. Both sensors have different interactions with the surfaces presenti in your study area. None of them is correct, nor false. But generally, L-band is more resistent to temporal decorrelation. As you see in your screenshots, coherence is not ideal in your image. The higher the coherence (and at best over large areas) the btter is the quality of the phase information to be expected. But there can still be atmospheric artifacts in the data.
The elevation you show in the screenshots (bottom right) is probably the one SNAP outputs from the Terrain Correction step. It is important to distinquish the one created as result of the InSAR DEM process and the one automatically downloaded as ancillary height information. Please have a look here: Using VV and VH to make DEM
Hi again.
I pre-processed my DEM (mosaic, clip). After that, DEM height difference is changed. Now ALOS, Sentinel DEM are same as each other.
What happened on this? Especially, height range
as I explained above, this is not your InSAR DEM. This ist just the SRTM which was used in the range doppler terrain correction step (same for both data).
Please read my comments here: Using VV and VH to make DEM
I have already created a DEM of my AOI (Nassiriya) with a couple of sentinel-1 images (perpendicular baseline = 30.43 m; temporal baseline = 12 d). Beside the low baseline, the coherence is very high
I applied the well-known steps, but the output DEM shows reversed and wrong height values, as I can verify on GIS, where I have also computed the hillshade. Here below my results: