@ shishir.manandhar
But I think I figured this out. So basically I terrain corrected 1)Displacement 2)Unwrapped phase.
And then I collocated them (stacked), and then I applied valid pixel expression of coh>0.4 on the displacement. And I believe the result is good. What are your thoughts on this @ABraun?
Here i given as shown in above figure.
Valid pixel validation : Unw_Phase_ifg_21Nov2017_27Dec2017_VV_slv1_21Nov2017>0.4
Is it correct for assigning the coherence value >0.4 ?
Then i created for all 5 interferograms in same way, finally stacked.
i want to know the displacement for that i added this displacements using Band Math, using this below command in edit expression.
($26.displacement_VV + $26.displacement_VV_slv2_27Dec2017 + $26.displacement_VV_slv4_20Jan2018 + $26.displacement_VV_slv6_25Feb2018 + $26.displacement_VV_slv8_21Mar2018)/5
but I’m getting this below error, please check it once.
masking by coherence is a good idea. Maybe you should include all displacements and coherence bands in one stack and then create an average coherence first and use this as a final mask (maybe with a lower threshold, because the average will always be lower).
you enter it in the valid pixel expression (remove what is already in there).
But I actually meant to have all coherence bands in one stack so you can calculate an average coherence as well which you can use for the masking of the average displacement.
I applied coherence for all the displacement bands as shown in above, then stacked all the bands (1+2+…19). But creating the final displacement band in Band Math i’m getting below error.
I created combined stack of only displacement band (1+2+…19), using this created one average displacement band using Band Math(dis1+dis2+dis3+…dis19)/19.
And then same way i created combined stack of only coherence band (1+2+…19). using this created one average coherence band using Band Math (coh1+coh2+coh3+…coh19)/19.
Then finally i stacked both of this bands.
properties of the displacement band (new_band_14), placed coherence band value (new_band_13_slv57_21Nov2017) >0.35 as shown in below figure.
Phase to Displacement
The unwrapped phase is now a continuous raster but not yet a metric measure. To convert the radian units into absolute displacements, the Phase to Displacement operator (under Radar > Interferometric > Products) is applied. It translates the phase into surface changes along the line-of-sight (LOS) in meters. The LOS is the line between the sensor and a pixel. Accordingly, positive values mean uplift and negative values mean subsidence of the surface (if the master image is the earlier acquisition date). Copied from InSAR Displacement Mapping with ERS data Issued April 2020 Andreas Braun.
Please clarify this one.
Because if LOS is increase (means sensor to ground pixel distance increases (+ indication)) I’m getting subsidence (- indication) and vice versa.