ASF HyP3 Support

[forrestfwilliams]

The ASF HyP3 on-demand InSAR service is great option for creating interferograms, but MintPy is not currently set up to ingest these products. I propose creating a prep_hyp3.py workflow that would allow for the ingestion of these products. I'm happy to perform this work, but could use guidance on preparing metadata.

[forrestfwilliams]

HyP3 product are projected to the local UTM zone. I imagine this could cause issues for the LAT/LON_START and LAT/LON_REF1/2/3/4 attributes. Can MintPy accommodate this, or must they all be reprojected?

[yunjunz]

No need for re-projection. MintPy should be able to handle X/Y_STEP = meters and its corresponding X/Y_FIRST.

Since most of the operations in mintpy do not care about coordinates, special attention to the coordinate system is only needed during geocoding and plotting in map coordinates, as far as I remember. Both of these two functionalities have been tested before, but not maintained via regular testing, so some functionalities may not work out of the box. But they should be fixed easily.

[yunjunz]

A HyP3 + MintPy support would be awesome @forrestfwilliams. I am not familiar with HyP3 results. Here is a general guideline to prepare datasets for MintPy: https://mintpy.readthedocs.io/en/latest/FAQs/. I am more than happy to answer any question you may have related to mintpy.

[forrestfwilliams]

Thanks @yunjunz! Currently HyP3 only provides the average perpendicular baseline, and not the baseline for the top and bottom of the interferogram. Should I see if I can get this data, or is it permissible to have the same average baseline for both P_BASELINE_TOP_HDR and P_BASELINE_BOTTOM_HDR?

[yunjunz]

Use the same value is perfectly fine.

[forrestfwilliams]

Hi @yunjunz, I've successfully created a prep_hyp3.py file that generates the needed rsc files for each interferogram. Hyp3 provides interferograms as tifs that can be viewed using view.py, but once an rsc file is generated for an interferogram, I believe that readfile.read assumes that the interferogram is now in a binary format, which causes an error and the message: "Unknown InSAR processor: hyp3". Do you have any thoughts on how to correct this?

[forrestfwilliams]

Disregard the previous comment, I was able to track down the error.

[yunjunz]

The discussion on the GMTSAR support (#452) could be a good reference here. We have implemented it here: https://github.com/yunjunz/MintPy/tree/gmtsar.

[yunjunz]

Here is the to-do list I could think of for full support of HyP3+MintPy workflow:

1. The 2D matrix of pixel-wised incidence angle [required for tropospheric correction and DEM error correction].
2. The connected components for each interferogram [optional but recommended; required for unwrapping error correctoin]
3. A 2D matrix of water/land mask [optional but recommended]
4. Add attributes: HEIGHT (satellite altitude in m) and EARTH_RADIUS, both of them are currently hardwired in the code here.

[talogan]

Thanks for the to-do list. We are going to start looking into this soon.

I note that the first link in this issue is to HyP3 version 1, which is our beta system. We've recently released our InSAR GAMMA process in HyP3 version 2, a more stable system that can be accessed through the ASF Data Search engine Vertex, through an API, or though a python SDK.

Documentation for HyP3 v2 is available at the HyP3 docs website.