Terrain correction and coregistration

Microwave Toolbox
#1

Hello everyone,
Which order is better for pre-processing two sentinel-1 images in the same area at different times: applying Terrain correction first and then apply Coregistration, or vice versa?
Thanks!
Hung

#2

depends on if your data is from the same track or from different tracks

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#3

Thanks. It is from the same track, so which order should I apply? and why?

#4

then you calibrate them to Sigma0, then apply Coregistration and terrain correct the stack in the end.

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#6

Thank you so much. But can you please tell me why we don’t apply Terrain correction before coregistration in this situation?

#7

because coregistration provides a more accurate alignment of the single images (at sub-pixel level) and you potentially lose some of this information when the data is resampled during the terrain correction.

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#8

Pardon me for a further question: why do we have to do the opposite in the situation of the images from different track?

#9

images of different lootracks cannot be coregistrated because the matching of points often fails due to the different looking directions. In such cases, a solution is to terrain correct first and select “Product Geolocation” as offset method, so that SNAP already “knows” which pixels roughly belong together.

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#10

Thank you so much for your clear explanation!