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SWOT_ATBD_L2_HR_PIXC: Request for PHASS [2017 WU] phase unwrapping algorithm
Posted: Wed Apr 16, 2025 5:10 am America/New_York
by jimmyaaa
Hello, I am currently learning the official document: JPL D-105504 L2_HR_PIXC Algorithm Theoretical Basis Document. In the UnwGeoloc module, the SpatialUnwrap section uses two two branch-cut based algorithms: PHASS [2017 WU] and SNAPHU [2000 and 2001 Chen]. I would like to study the details of the algorithms, but could not find the source of PHASS [2017 WU]. Could you provide the information? Thanks.
Re: SWOT_ATBD_L2_HR_PIXC: Request for PHASS [2017 WU] phase unwrapping algorithm
Posted: Thu Apr 17, 2025 1:05 pm America/New_York
by PODAAC - jmcnelis
Hi jimmyaaa,
We forwarded this request to the subject matter experts from SWOT. We'll follow up with you here ASAP.
Thanks,
Jack/ PODAAC
Re: SWOT_ATBD_L2_HR_PIXC: Request for PHASS [2017 WU] phase unwrapping algorithm
Posted: Mon Apr 21, 2025 12:25 pm America/New_York
by PODAAC - jmcnelis
Hi again
@jimmyaaa,
This is the response from the SWOT SMEs:
The inline reference to “[WU 2017]” in the L2_HR_PIXC ATBD refers to a JPL internal document that is unfortunately not available publicly. The reference was supposed to have been removed from the ATBD, but it was inadvertently left in the body text of the document even though the full citation in the list of references was indeed removed. The PHASS algorithm is an implementation of a minimum cost flow (MCF) phase unwrapping algorithm [see Costantini, 1998]. That is, the PHASS algorithm treats the phase unwrapping problem as a congruent, L1-norm network optimization problem [see discussion in Ghiglia and Pritt, 1998 and Chen and Zebker, 2001]. Many solvers using network programming approaches are available to handle this type of optimization problem, and PHASS uses a specific approach that is chosen for its computational efficiency. The code for this algorithm is not available publicly, however.
M. Costantini, “A Novel Phase Unwrapping Method Based on Network Programming,” IEEE Transactions on Geoscience and Remote Sensing, vol. 36, no. 3, pp. 813-821, May 1998.
D. C. Ghiglia and M. D. Pritt, Two-Dimensional Phase Unwrapping: Theory, Algorithms, and Software (Wiley, New York), 1998.
C. W. Chen and H. A. Zebker, “Two-Dimensional Phase Unwrapping with use of Statistical Models for Cost Functions in Nonlinear Optimization,” Journal of the Optical Society of America A, vol. 18, no. 2, pp. 338-351, 2001.
Please let us know if you have additional questions. Thank you
Jack