Combination of raster subset and merge

snap
1

I have an AOI whitch sits right at the border of 2 sentinel-1 GRD tiles. It is situated in the sea (not terrain)

There are multiple questions regarding the preprocessing of data in such situation.

  1. should I first stich/merge the two S1 tiles and then crop/subset the AOI window ?

  2. Should I crop/subset the interesting area from individual tiles and then merge the cropped subsets together?

I ask this as I think depending on this first step many SNAP preprocessing functions might not work properly in subsequent steps.

In addition as I noticed, when you try to merge two tiles, It could heavily change the statistics of the pixels (figure bellow):

Screenshot 2026-01-19 122031
Screenshot 2026-01-19 122031891×945 134 KB

2

Based on your post under Microwave Toolbox, I assume the two GRD products are used for oil spill detection. Therefore, I also assume the two GRD products are acquired at the same day and from the same track. In that case, I think you should preprocess each product with calibration and speckle filtering, then merge the preprocessed products using S-1 Slice Assembly operator. After that, you can subset the image to your AOI and perform oil spill detection.

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3

Your assumptions are right. But the AOI is considerably smaller than the size of two S1 tiles. In addition I have a total number of 40 days of data to process (2 tiles per date). I was hopeful to cut the processing time by first subseting the inputs and then go through the other preprocessing steps as I want also to benefit the GPF and its batch processing tool.!

4

That should work too. Good luck with your oil spill detection project.

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5

That should work too, Good luck with your oil spill detection project.