Understanding difference between collocation and coregistration

Question

I'm a little confused on this topic. I need to put 2 SAR images into same coordinate grid.

In ESA SNAP tool, there are 2 options:

• coregistration: Radar->Coregistration->Coregistration
• collocation: Raster->Geometric Operations->Collocation

SAR images are from COSMO-SKYMED and ALOS1 missions.

What is the conceptual difference between collocation and coregistration?

Answer 1

You should prefer coregistration since you will use different type of SAR images. Collocation can be used if the images are in the same coordinate system or two spatially overlapping products (similar to layer stacking).