SNAPHU Unwrapping


Hi gabs,

I will see deformation in volcano area, so I used Snap for processing PALSAR images, and did same way with the tutorial given. but the result is not so good. what do you think about this problem.



Hi again,

Do you have used Sentinel 1 images? I did an displacement map of deformation in Santa catarina Do Fogo volcano, this is the results

I recommend you!!!


this is interesting. Which dates did you chose?


Hi ABraun

I used images with dates Nov, 03 and Nov, 27 2014.


alright, thanks - I guess there was an Eruption in between?


Yes, its last eruption was Nov 23 2014.


Nice work, it sucseeded me to :slight_smile:



before unwrapping i need some noise correctionā€¦I tried it with band math:

  1. i need to compute the coherence map coh(coh<0.4)=0
  2. to reduce the noise, after goldstein filtering in the PhaseBand:
    coh * Phase_ifg_srd__15Nov2015_23Aug2015

The problem is, this creates two new bands, which will not be processed by the SNAPHU export option of SNAP, so how can I fit this new bands into SNAPHU?

Because obviously I donā€™t find a way to just edit/make changes on the actual coh and phase bands.


Dear osvaldoguax, how can I check coherence value in Sentinel 1 Toolbox or SNAP? I have experience with GAMMA and it is very easy to use but I still have trouble using Sentinel 1 Toolbox or SNAP. Could you enlighten me?


Hi glenn, could you give us the steps you use to make the DEM?


Please consult the toolbox help and tutorials.


dear osvaldoguax,

which area is it? Is this area vegetated area (forest, plantation or others) or is it non vegetated area?


olvaldoguax congrats for your workā€¦ which process did you use in SARScape?


Hi everyone!

I am assessing subsidence process in a region at Brazilian Northeast using Alos PALSAR (six interferometric pairs).

I followed all steps according to this tutorial:

Evaluating the Phase Unwrapping generated by Snaphu (after a long time to processing), I think there is something wrong:

  1. The most of pixel values are incoherent, I thinkā€¦ (see histograms);
  2. The presence these patterns of gradients in the images;

With these pixel values, the results of Vertical Displacements are inconsistent!

Someone can help me?



Hi ElmoTanajura, I did same work with ALOS PALSAR images, but I not get goob coherence, my dataset of Palsar, had high decorrelation spatial and temporalā€¦


Hi Gabriela!
In general the coherences were moderate. In the images 1 and 2, betterā€¦


Hi ElmoTanajura

I recommend you must continue searching pairs interferometric with high coherenceā€¦ because the pairs with low coherence not give you good results!!!

I yet continued searching my pairs!!!


After unwrapping the interferogram, I find the tiles with discrete value in the results. Why?
Here is the interferogram:

and the unwrap phase:



The reason might be the corregesteration step, especially when the study area is located in to two bursts,
So, is your study area located in one burst or two bursts?


if the errors only occur in the unwrapped interferogram but not in the original interferogramm it must have happened during the unwrapping.
Which parameters did you chose? TOPO or DEFO?