Low Temporal Coherence

[Ritwika Dasgupta]

Hi all,

I ran smallbaseline app on my interferograms created using SNAP (Sentinel 1A).
My temporal coherence is coming out to be very low overall and my area of interest was getting masked out. So, I set mintpy.networkInversion.minTempCoh  = 0.

Can someone suggest how my outputs can be improved or what could have gone wrong?

PS- I'm very new to mintpy as well as SAR in general.

Attaching the pic folder here - https://drive.google.com/drive/folders/1GxWkhE7A3rAFnQA5WOCHzxy4V-9EO_Q8?usp=drive_link

Thanks in Advance.

[Manudeo Singh]

Hi,

Your average coherence values are very low, even for 6-days apart acquisitions. What multilooking values are you using for InSAR stack generation? Try increasing that value and regenerating the stack. 

Best,

Manu 

_________________________________
Dr Manudeo Singh
Royal Society - Newton International Fellow
Department of Geography & Earth Sciences
Aberystwyth University, Wales, UK

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[Eric Fielding]

Hi,

I checked the location of your study area using the KMZ and it is in the tropical area where C-band InSAR has low coherence. As Manu suggested, you can take more looks. You can also try to get L-band SAR data.

++Eric Fielding

JPL

[Ritwika Dasgupta]

Thankyou so much for your replies Manu and Eric.

I'll try out these methods. 

@Eric - can you let me know if I can get L-band SAR data for free from somewhere? 

I tried looking for this in ALOS 2 but could only find few scenes which were free to download. I'm not sure if I'm doing something wrong here.

[Eric Fielding]

Hi Ritwika,

Yes, JAXA is only making the ALOS-2 ScanSAR data available for free download, and there is much less data acquired than with Sentinel-1. It looks like you went to the JAXA G-Portal, which is the right place to look. In most locations, there is more ALOS-2 data acquired between 2015 and 2018 than after 2019 when they reduced their acquisition frequency in many areas. We are trying to get the NASA-ISRO SAR (NISAR) mission launched in the next few months and it will provide L-band data every 12 days over all land.

++Eric

[Eric Fielding]

Hi Ritwika,

For Sentinel-1, I would recommend 19 range and 7 azimuth looks in this tropical area.

++Eric