Dear all:
Is it possible make a substraction between two correlation images to see changes in the surface, for example, before and after the earthquake (viewing correlation image before the earthquake and correlation image in coseismic rupture). E.g. (NASA,Applied Remote Sensing Training Program)
this is possible in SNAP. It tells you where surface characteristics changed for a given time. You need three images:
A: before earthquake
B: before the earthquake
C: after the earthquake
AB and BC should have have the same temporal baseline, e.g. 12 days, to make them comparible and exclude the effect of temporal decorrelation.
- Coregister AB (stack1) and BC (stack2)
- Compute coherence for both stack1 (coherence1) and stack2 (coherence2)
- Terrain correct both stacks
- Stack both terrain corrected coherence products into one product
- Apply band maths to subtract coherence (coherence2 - coherence1) to get the difference image shown above.
- Use a suitable color scale and range in the color manipulation tool.
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