Subtract Topographic Phase using snappy

Microwave Toolbox Interferometry
#1

Hello,
I’m currently trying to calculate an interferogram using snappy.

parCoh = HashMap()
parCoh.put('subtractTopographicPhase', True)
parCoh.put('demName', 'Copernicus 30m Global DEM')
coh = GPF.createProduct('Interferogram', parCoh, tss)

The code runs with no errors but the topographic phase subtraction does not seem to be working. I suspect the parameters are not correcly defined and i’ve tried many variations.

image
image1536×931 308 KB

Left: python image, Right: manual snap image

I’m posting here after not finding answers online.
Does anyone know how to solve this problem?

Thanks in advance

notes:
snap version 8.0.9
python 3.6

#2

Looks like the coherence estimator window size is different, at least.

#3

Hi,

In both cases, I didn’t change anything related to the window size.
However, on the left side image I used a Terrain Correction with a “Pixel Spacing” of 20 m, while on the right side image I used “Pixel Spacing” of 13.89 m (default value).

#4

I had a similar issue and fixed it by setting the ‘coherence range window size’ and ‘coherence azimuth window size’ parameters when generating the interferogram. This produced a coherence image that matched the resolution when I did the processing using the SNAP gui.

The code I used for these parameters:

    params = HashMap()
    params.put('cohWinAz', 3)
    params.put('cohWinRg', 10)
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