Differences between "Coregistration" and "DEM-Assisted Coregistration"

Hi there!

Under the “Radar----Coregistration” button, there are two optional function:

(1) Coregistration
(2) DEM-Assisted Coregistration

My questions are:

A: What are the differences between the two ways of coregistration?

B: I am using ALOS-2 L1.1 SLC data to do offset tracking analysis, I want to use SNAP to firstly do image coregistration, and than move to other software to perform offset tracking. Which way of coregistration in SNAP should I choose?

PS: I am using an interferometric pair of SLC data. Same orbit, same look angle etc.

Thanks for any help!

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The difference between the two coregistration is that the first one (coregistration) is based on a double cross correlation of images (coarse then finer). It has the advantages of needing no external input.

The DEM-Assisted Coregistration is based on orbit files and DEM. I suggest you to read the following article which clearly explain the method : impact of dem-assisted coregistration on high-resolution sar interferometry
http://ieeexplore.ieee.org/document/5613931/
The idea is to find an analytical expression of the pixel’s shift between the images caused by the topography. It thus requires an external DEM.

For you second question I don’t know. The first method gives you “poor” results. However, if the orbits are not precise enough, the second one cannot help you much.

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