I’ve followed all the Sentinel-1 tutorial of 2014 Napa Valley Earthquake. The results, geocoded interferogram and unwrap phase, are exactly the same as ones shown in the tutorial.
However, after using ‘phase to displacement’ on unwrapped result. The displacement is a bit strange.
According to Earthquake detail in USGS website, it should be a right lateral fault with strike 155 degree.
Their InSAR displacements are opposite of what I got from SNAP.
I would like to ask whether I’ve done something wrong or I misunderstood something regarding LOS and displacement from the ‘Phase to Displacement’ process.
I must use ‘Phase to Displacement’ not the unwrapped-only one to determine the displacement caused by an earthquake, right?
are you using the latest version of SNAP? I remember a similar error with inverted result scale which was caused by a deprecated version. Unfortunately, I can’t find the topic at the moment.
Your result does look like the example to me however, just with a slightly different colour ramp.
I’m using the latest one (SNAP 5.0 with desktop and engine implementation version 5.0.4) on Windows 10.
And yes, I notice a different colour around the lower right lobe of the unwrapped one too.
now I notice the difference at the lower right. Seems that it wasn’t handled correctly by the unwrapping.
One reason for that could be that the snaphu export wasn’t as developed as today and because of that some parameters may be different (number of tiles, for example).
If you had the chance to look at the config file of the tutorial you could compare if the same settings were used.
<img src="/uploads/default/original/2X/7/7d5f6da294b46b264694a5bf6e3d708fbb25e7e9.png" width=“500” height="450>
Sorry for a late reply.
The one you shown is the default parameter from the program and I have used them.
Now I’m trying to change the clipping (subset area) to see whether it would affect the result
and maybe other values like the numbers of rows and columns.
Dear Dr. Luis Veci/ Dr. ABraun
I can not find Napa Valley data: 7 and 31 August 2014 for Napa Valley Earthquake.
Thank you for your attension.
I’ve changed a scale to match the USGS’s.
I wonder about the definition of ‘Line-of-sight displacement’. Not sure if I understand it right.
On SNAP, InSAR result comes from [Master (Before) phase] - [Slave (After) phase]. So, for an absolute phase (unwrapped but before doing ‘phase to displacement’), does a positive value mean moving toward a satellite?
However, for LOS, some papers use the arrow point away from satellite (from antenna to ground), but some use the arrow point toward the satellite. This would make positive ‘displacement’ value means away or toward a satellite, respectively. Which case is correct?