Terra-SAR Phase information


Regarding damage detection in urban area using TerraSAR-X data;

I have three TerraSAR-X images with resolution 2.62 m of orbit 39.

To derive the phase:

  1. I creat two stacks:
    First stack: (first & second) images,
    second stack (second and third) image

2.using SNAP=>Interferometric=>Product=>Interferogram Formation=>Topographic phase Removal=> Goldstein Phase filtering.
For first stack the phase looks like noise
While the phase for the second stack looks very good

Kindly help me to figure out how I can derive a coherence phase for the first stack not noise as I have.


You have 6 years between your first and second images. I’m not surprise to see a total decorrelation due to this very high temporal baseline.

Probably also the Bperp is much difference. Sometime, even if it looks like noise, you should zoom in to see better. Do you have by change also the interferometric coherence computed?

Could you say which are the Bperp for both cases?

Yes may be this is the reason but I would say that the buildings/built-up areas must show a high phase coherence .

Do you mean temporal baseline by Bperp?
Yes the interferometic coherence looks like noise as well.

with Bperp I meant perpendicular baseline.
Normally TSX is controlled for taking orbits suitable for DInSAR.
Could you please provide more info about the processing of the noisy interferogram?

Actually I do not know how to calculate Bperp.
The processing to derive the interferogram
using SNAP=>Interferometric=>Product=>Interferogram Formation=>Topographic phase Removal=> Goldstein Phase filtering.

no further process has done after I got this noisy image

If you open SNAP from terminal, then this info is logged on the terminal screen. You can always open both images within SNAP and use the InSAR overview operator (same for selecting master image within a image stack) and get the Bperp information.

Thank you very much.
for the first stack:
the Bperp (m) is -53.09 m
and the Btemp (days) 2112 days

for the second stack:
the Bperp -20.17 m
and the Btemp -209 day

In such case it seems indeed that everything might be related to Btemp, but I am still not convinces. Which kind of environment are you working on? Urban? Rural? Montains? Agricultural?

I am working on urban area

Have both master slave images same beam/orbit/acquisition mode?

yes same acquisition mode SSC/same track 39

Then my only advice is to try to coregister the pair with other parameters. Or to visuallise the master-slave overlap on your area.