I’m newbie on Sentinel-1 and Lately I was struggle to produce a DEM from Sentinel 1 using Interferometric process in SNAP…
I have passed all step from the tutorial and power point training step by step documentation created by Michael Foumelis “Sentinel 1 TOPS Interferometry”, and I was succeed produced a DEM using SNAP.
but when I’m compared the data from Sentinel-1 Insar result with SRTM 3 Arc, the result was exactly the same, there is no difference between Sentinel-1 Insar and SRTM
See my comparison preview in pic above bottom part:
My question are ?
Do the DEM file in the SNAP “Elevation” band that I produced is really data from Interferometric or just another copy of SRTM?
Which one should I export Elevation_VV Band or Elevation Band to produce a DEM??
My Elevation_VV preview is something like in the preview above second from above:
Is my Elevation_VV correct? what I’m missing?
What is the Maximum DEM Resolution can produced by Sentinel-1 with Sensor Mode IW.
Here I have two DEMs: InSAR elevation obtained after interferometry anf SRTM. I used SRTM 3ArcSec to produce InSAR dem. So, it have to have close value of elevation value. But you can see on this screenshot that the value is different on more than 20m. The value is taken from the pixel corresponding a lake. Nothing have change after almost 20 years - the same lake on the same territory. And such difference appears on all my InSAR DEMs.
Why it could happen: values of two DEMs built from the same source are different on 20m.
InSAR generates relative topographies which are then leveled to a surface using a DEM. Accordingly, there can be differences between the InSAR DEM and the outcome due to low coherence, atmospheric disturbance or unwrapping errors. Please have a look here, especially chapters 3.4 “From phase to elevation” and 3.5 “Error sources”: http://www.esa.int/esapub/tm/tm19/TM-19_ptB.pdf
I read this handbook. The situation is troublesome because such difference in 22-25 meters is constant for every SLC pare. Moreover, for every territory investigated + on every computer + for every operator (I am working in group). Can you explain, on which step relative topographies leveled to a surface using DEM (if I understand your firs sentence right)? I thing it leveled at the step “Terrain Correction”, didn’t it?
Here I show the coherence
I had same issue, with 40m of elevation difference between true elevation and S1 SLC. My professor guessed, that 40m is actually the height above the geoid, in my AOI. So i added a new line to snap properties “snap.useDEMGravitationalModel = false” and made a new elevation model and it worked.