licsbas decompose:cumulative displacements from ascending and descending orbits

[stallinbhandari]

hi yumorishita, I got the cumulative displacements from both ascending and descending orbits. but the values have high discrepancy (Asc.-> -404 to 64 and Dsc.->-237 to 74)mm for Kathmandu, Nepal. Is it rational or not? do they differ to that extent? The final decomposed values for components EW =-17 to 109 and UD =-400 to 82. What shall I do for the NS component?

[yumorishita]

The difference between asc and des could be rational because they contain different deformation components (opposite contribution from horizontal deformation). The NS component cannot be obtained only from right looking because of insensitivity to the NS deformation.

[stallinbhandari]

And, how can we validate the results? can we convert the GNSS data onto the LOS vector? how?

[yumorishita]

You can project GNSS 3D (EW, NS, UD) deformation data to a LOS direction by multiplying LOS unit vector components (E.geo, N.geo, U.geo) and summing them.

[stallinbhandari]

can i do it this way? first converting the U.geo file to tiff then multiplying the U.geo.tiff with the UD component of GNSS in a GIS software?

[stallinbhandari]

both the asc. and dsc. frames have U.geo file. Which one should I use?

[yumorishita]

Asc and des have different LOS. You should convert GNSS 3D deformation to asc and des LOS respectively. You need E/N/U.geo in both orbits. I suggest reading the E/N/U value at the location of GNSS points from E/N/U.geo using GIS software. Then multiplying and summing them (i.e., calculate the inner product of the GNSS 3D deformation vector and the LOS unit vector).

[stallinbhandari]

Can we compare the EW and UD components from LiCSBAS_decompose output with the vertical component of GNSS measurement?

[yumorishita]

Yes, UD from LiCSBAS and vertical GNSS are comparable. We should note the reference point.

[stallinbhandari]

the cumulative displacements for ascending and descending data are for two different time periods. The deformation of which time period is given by the LiCSBAS_decompose output?

[yumorishita]

It depends on the input LOS deformation files you used.

[yumorishita]

If you used different time periods for asc and des, the decomposed deformation has no particular time period. You must assume something (e.g., no deformation between... or constant velocity)

[stallinbhandari]

in my case, the study area has a tectonic movement of 4cm/yr in NE direction, does this influence my results?

[yumorishita]

It depends.

[yumorishita]

This question is not about LiCSBAS software, but general InSAR knowledge. Let me close this issue.