Sentinel 1 Displacement Calculation

Microwave Toolbox
#1

Hello there,

I´d like to try whether I can detect displacement movements in a permafrost region working with S1_SLC_IW data. I succesfully preprocessed and stacked a couple of images for the time from Januar to March and also did the same for images with acquisition dates during Juli to September. I thought with that I can compare displacement patterns that occur during due to the freezing and thawing processes during the chosen month. My problem is that I get an Error that the Stacks do not overlap, even though I used the same sub-swath and burst for every image and created the same subsets.

Can anybody help me or explain me how this can be?

Best regards :wink:

#2

what oprator did you use to stack the results and what exactly was the error message?

#3

I used the Create Stack Operator. The error message is that my “product has no overlap with the master product”.
I did most of my steps following an ESA TOPS Sentinel 1 Tutorial. The coregistration of my image pairs the unwrapping and everything went fine. As it was recommended to analyse a series of images in order to minimize the impact of atmospheric phase disturbances or unwrapping errors. Also the stack of those image pairs with the Create Stack Operator went well. My final idea was to compare one stack during the winter period with one image stack of the summer period. I also tried clipping the stacks to the exact same subset but it still says there is no overlap. I also tried to average the each stack to minimum values and then tried to stack my two stacks again but it still did not work. Or maybe there is a totally different way to calculate displacement that might occur between winter and summer term?

#4

so did you apply Terrain Correction at the end of the pre processing of every product? After that, stacking should be no problem.

#5

Yes I did apply the Range-Doppler Terrain Correction.

#6

maybe you selected different coordinate reference systems for the stacks?
This could explain why SNAP thinks that they do not overlap

#7

When I did the Terrain Correction is chose the WGS84 map projection for both stacks.

#8

are the extents of the different products visible in the WorldView or WorldMap window?

#9

Oh my god I am felling so stupid right now. The extents are visible but did not match. I thought they definitely match as I chose the same sub-swaths and the same burst, but it occurs that I have to chose slightly different bursts for summer and winter imagery. Now they match and it works. Thanks a lot!

#10

no problem - glad it works now!

#11

Hello Sir,
I hope you can help me,
I have already generate displacement map by SNAP, which have negative values.
my question is : How can I know the nature of the mouvement (near or far from the satellite)?