Coherence Mask/Threshold for Unwrapping

like invert the value of each band in the bandmaths ? I am not sure I understand
I try to change the value, exchange the name but it doesnot work for snaphu .

what happens if you delete the original phase before exporting? Of course the phase from band maths should then be renamed accordingly.

That is why I ask if I can copy the band with its values. If I delete the original band the new one does not work because its values are linked with the original band

just create a new band with the same values in the band maths. The expression is the name of the band, remove the ā€œvirtual bandā€ checkbox.

Yes but it is the same. I am creating a new band which has the value of the previous created band using the original phase value. So if I delete the first one nothing is working after. I tried with virtual and not.

if the band is not virutal it should be independent from the original. Did you include all steps?

  1. Copy band
  2. Save product (File > Save product)
  3. Delete original
  4. Open copied band

I will try again to be sure and Iā€™ll tell you.

So I have create the new band ,made it not virtual, saved the product, remove the original. Until now fine I still have the new band. I can export, snaphu is fine but canā€™t import because already the i_band

how did you name it before exporting? I donā€™t get the i_band issue.

for the new phase I put the original name of the phase.
Actually I passed the first part that was saying error with the maginary band and launched the import snaphu with the error and it worksā€¦ donā€™t know the difference with yesterday but it is working.
Sorry and thanks !!

Actually I still have a problem.
Except the one that work on friday, my interferogram products present one phase band and one phase srd band. Why is that ? If I delete it the unwrapping does not work and if I let it this band is unwrapped and not the one that I created with the the coherence mask.
Thanks

Itā€™s been a while since that question, but Iā€™m trying to do the same (masking out pixels with low coherence before unwrapping, have you solved this @MarineROGER ?

A method which seems to work was suggested here: Is it the right way to create mask for phase unwrapping?

Many thanks, it improved!

Cool, would you mind sharing the result and how the masking improved it - kind of a before/after?

Yes!


Left DEM without coherence and water mask, right with masks. It improved because ablation area of the glacier can be seen in the right DEM.
The place is in the Andes ice field, Viedma glacier, it has very low coherence because of water, bad weather, vegetation and moving ice.

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Can we mask areas of the interferogram band that are corresponding to the low coherence pixels in the coherence band?

Edit, Sorry, I figured it out. We just have to type the expression coherence > 0.4 , or whichever value of coherence, into the properties of the wrapped phase layer, not in the properties of the coherence layer but we should make sure that both coherence and phase layers are in the same product

But. Is there a way to completely mask low coherence areas from water bodies based on the waterā€™s zero elevation value from a DEM?

because masking out the water bodies based on the coherence values will also mask out some areas of the land with comparable coherence values

you can combine statements in the valid pixel expression, e.g. coherence > 0.4 and elevation == 0
Not sure about the correct syntax, but it is possible.
But you have to do it as described here: Filter out low coherence pixels before phase unwrapping