Dear friends,
I have found subsidence using two images in year 2016 and two in 2017. I have placed 24 pins on the displacement map of the year 2016 and exported the values in a table having following coulmns Sr No. Pin Name X Y Longitude Latitude Coherence (coh) Displacement (meter) with coh >= 0.4
Now i wish to show the displacement at the corresponding points with identical X, Y, lat, long’s for the year 2017. so that displacement value at every pin position can be compared year wise.
Please guide how to import or export values at same pin positions in the two maps?
regards
if you have created pins in one product, you can export them in the pin manager with this button and write them to a XML file.
Then you process your second image pair as the first and use the import function in the pin manager again where you select the XML file.
Then you export the values of the given rasters again.
Thanks i got it.
One more query;
I have taken S-1A data for one year and S-1B data for another year with 44.88 and 44.35 perpendicular base line and 96 days temporal difference.
Would it effect the results?
my results seems twisted clockwise. why?
Sentinel-1A and 1B are fully compatible for InSAR, you can combine them. What is important is which date is selected as master and which as slave as this decides the direction of the movement (towards or away from the sensor) .
Makes sense, but specifically in which direction does this shift occur based on mst/slv date?
Example An ifg was calculated with two images in reverse date order:
September2017 Master and August2017 Slave results produce positive phase to displacement values and positive vertical displacement (heaving) via band maths calculations. Correct?
Or should these values be multiplied by -1 to indicate negative vertical displacement (subsidence) due to the temporal reversal of the images?
Thank you.
In searching the forums I found several seemingly conflicting or vague responses on this matter.
Dearfriend,
I have created a stack of 12 interferograms (split_orb_coregi_ifg_deb_dinsar_ml_flt_avg). Now i wish to export it to Snaphu, it gives an error saying product should be co registered. when i export (split_orb_coregi_ifg_deb_dinsar_ml_flt) to snaphu all products are exported. Now how can i run phase unwrapping of all products?
I have to go for phase to displacement in the end.
sorry, I don’t understand: Did the export work or not?
As far as I know, snaphu only works on image pairs (not stacks).
So the best way to process Sentinel-1 images is to create pairs by TOPS coregistration, create the interferogram, deburst it and export it to snaphu.
Then process each interferogram individually as shown here: https://www.youtube.com/watch?v=sH4Uhsgmpak
Then import the unwrapped phase (select the hdr file) back into SNAP. You can perform “phase to displacement” on this product then and finally terrain correct it.
I was preparing stacks for StaMPS, the i found a flow for stacks SNAPHU export. Thought i should give a try. Please look at the end of this doc. _Prepare for STACK AVERGING for its authenticity.
referring to this document: Preparation for StaMPS is one tutorial and Export for stack averaging is another approach. They are not referring to the same workflow or analysis.
thanks Abraun.
It had troubled while making a stack of 32 images so i break them in three stacks and planed to merge them after stamps export.
I have created 3 coregistration stacks for 2016(8),2017 (12)and 2018(12) images with single master (9/9/2017)
Steps taken are:
split; apply orb; backgeocoding; added LAT LON bands using bandmath; deburst ; subset
Final product: 1. subset_master_stack_2016_deb
2.subset_master_stack_2017_deb
3.subset_master_stack_2018_deb
and then intefer;topo_phase_removal; add elevation band
Final product:1. subset_master_2016_deb_ifg_dinsar
2.subset_master_2017_deb_ifg_dinsar
3.subset_master_2018_deb_ifg_dinsar
Although i have not got all these products yet i mentioned here my plan of flow to go further. Trying backgeocoding for single stack of 32 images also. Will update this progress also.
Screen shots i shared are the result of stamps export of 2016(8)stack.
Are you working with dual polarizations? You can only use once for PS InSAR anyway so I recommend to select VV in the Split step and continue with this band only.
I cannot tell if this is the reason for the error however.
Another thing that can be shortened is the creation of lat/lon bands by band maths. If you check it in the interferogram step, they are automatically created in the exact format that is needed for the export.
Finally, if you really want to go sure to have the data prepared correctly, I can highly recommend the Snap2stamps package: a free tool to automate the SNAP-StaMPS Workflow
It basically performs all required steps in an automated and structured way: coregistering multiple slaves against one master and creates an interferogram which is then debursted.
yes Abraun its single burst IW3 VV polarization. Now i got 32 image stack interferogram result with Coherence range ans azimuth window size as 20 and 5. But processed products (Ifg and coherence are not opening) giving java error shown in screen shot.
Maybe from the subsetting? I don’t have an idea, sorry. Based on the error message alone, it could be anything. It is not related to anything SAR specific but just a generic Java message.
and write them to a XML file.
in the pin manager again where you select the XML file.
