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SARScape: How to estimate velocity from PSInSAR results

Mean velocity is an output parameter of the PS SARscape processing. It is available in .csv file after PSInSAR process.

The mean velocity represents the solution found during the inversion step according to the velocity range parameter.
The software simply applies a "Brute Force" algorithm by trying different velocity values to find the best fitting with the interferogram phases date by date.
Basically, the equations system solved during the first inversion is the following:  (linear model according to the PSI)

phase1= v*Time + K_fact*Residual_Height

phase2= v*Time + K_fact*Residual_Height

phase3= v*Time + K_fact*Residual_Height

phase4= v*Time + K_fact*Residual_Height

phase5= v*Time + K_fact*Residual_Height
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phase(N)= v*Time + K_fact*Residual_Height

Where N is the number of interferograms, v is the mean velocity(mm/year), Residual_Height(meters) is the height correction respect to the input DEM and K_fact depends on each acquisition, because it is a geometric paramter which depends on the baseline, incidence angle and slant range distance.

For each pixel, the pair( Vel, Residual Height) is found.
The multitemporal coherence (first and second inversion steps :_cc_first, _cc) generated together with the two unknowns is the index that measures the quality of the pair found.
The higher the value the higher the accuracy of matching interferogram phases and linear model.

Ferretti, Alessandro, Claudio Prati, and Fabio Rocca. "Permanent scatterers in SAR interferometry." IEEE Transactions on geoscience and remote sensing 39.1 (2001): 8-20.

- Created by MM 12/5/2022; review by BC 12/07/2022