problems in geocoding wrapped interferograms in complex type

[comma-never-coma]

Description of the problem
I am trying to geocode ISCE-2 interferograms using geocode.py, and I just run the example commend obtained from geocode.py as follows.
Full script that generated the error

geocode.py filt_fine.int --lat-file ../../geom_reference/lat.rdr --lon-file ../../geom_reference/lon.rdr

The program runs successfully, however the wrapped phase in a geocoded interferogram is incorrect. Phase values after geocoding change into 3.14, which is the same as pi. Give the interferograms below.

And there appears some unexpected messages ComplexWarning in the terminal, this is the output:
Full error message

No lookup table info range/lat found in files.
number of processor to be used: 1
resampling software: pyresample
read latitude / longitude from lookup table file: ../../geom_reference/lat.rdr
output pixel size in (lat, lon) in degree: (-0.00031570278911694004, 0.00032012760497859225)
output area extent in (S, N, W, E) in degree: (33.464494425028974, 33.96488334577933, 112.49700943082642, 113.56847652468977)
output file row / column number: (1585, 3347)
--------------------------------------------------
resampling file: filt_fine.int
--------------------------------------------------1/1
reading complex in block (0, 0, 2550, 1423) from filt_fine.int ...
nearest resampling with pyresample.kd_tree using 1 CPU cores in 6 segments ...
/home/comma/miniconda3/envs/isce2/lib/python3.9/site-packages/pyresample/kd_tree.py:824: ComplexWarning: Casting complex values to real discards the imaginary part
  full_result[valid_output_index] = result
/home/comma/miniconda3/envs/isce2/lib/python3.9/site-packages/mintpy/geocode.py:140: ComplexWarning: Casting complex values to real discards the imaginary part
  dsDict[dsName][block[0]:block[1],
write file: geo_filt_fine.int
write file: geo_filt_fine.int.rsc
write file: geo_filt_fine.int.xml
write file: geo_filt_fine.int.vrt
time used: 00 mins 1.5 secs.

According to the error message, I modified the line 823 in kd_tree.py and line 103 in geocode.py, to add dtype = 'complex_' while creating the matrix, just like:
full_result = np.ones(output_raw_shape, dtype = 'complex_') * fill_value # line 823 in kd_tree.py
dsDict[dsName] = np.zeros((res_obj.length, res_obj.width), dtype = 'complex_') # line 103 in geocode.py
Under the condition dtype = 'complex_', I got a correct geocoded interferogram with geocode.py as below:

At the same time, it would generate the same ComplexWarning under the condition dtype = 'complex_' if we try to geocode unwrapped interferograms or coherence maps whose data type is actually not complex. But the output data seems to be true although there is a ComplexWarning.

System information

• Operating system: Linux-Ubuntu
• Python environment: conda
• MintPy version: 1.5.0

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[yunjunz]

Thank you @comma-never-coma for the reporting and fixing! I am able to reproduce your error and solution. This is because mintpy (and pyresample I guess) was NOT designed to resample complex data arrays.

The following generalization of your solution should work. Could you please issue an pull request in both mintpy and pyresample for this?

• In mintpy, change mintpy.geocode.py#103 from:

                dsDict[dsName] = np.zeros((res_obj.length, res_obj.width))

to:

                dsDict[dsName] = np.zeros((res_obj.length, res_obj.width), dtype=atr['DATA_TYPE'])

• In pyresample, change pyresample.kd_tree.py#823 from:

    full_result = np.ones(output_raw_shape) * fill_value

to:

    full_result = np.ones(output_raw_shape, dtype=data.dtype) * fill_value

[comma-never-coma]

Thank you @comma-never-coma for the reporting and fixing! I am able to reproduce your error and solution. This is because mintpy (and pysample I guess) was designed to resample complex data arrays.

The following generalization of your solution should work. Could you please issue an pull request in both mintpy and pysample for this?

* In mintpy, change [`mintpy.geocode.py#103`](https://github.com/insarlab/MintPy/blob/1a3e85df8c855b97f9a745b7838023d369579e92/src/mintpy/geocode.py#L103) from:

                dsDict[dsName] = np.zeros((res_obj.length, res_obj.width))

to:

                dsDict[dsName] = np.zeros((res_obj.length, res_obj.width), dtype=atr['DATA_TYPE'])

* In pyresample, change [`pyresample.kd_tree.py#823`](https://github.com/pytroll/pyresample/blob/b8ecc7104cf132f10dee5438eb3049f526199013/pyresample/kd_tree.py#L823) from:

    full_result = np.ones(output_raw_shape) * fill_value

to:

    full_result = np.ones(output_raw_shape, dtype=data.dtype) * fill_value

Thanks for your suggestion! I have issued a pull request in both mintpy and pysample. I'm sorry because this is my first time to make a PR and I'm not sure if there would be something wrong.

[yunjunz]

Thank you @comma-never-coma, your PRs look good to me.