S1 TOPS Coregistration vs DEM Assisted Coregistration

[psoglia]

Hello,

I am struggling trying to understand the differences (if they exist) between S1 TOPS Coregistration and DEM-Assisted Coregistration.

Looking at the help, they seem the exact same thing:

S-1 TOPS Back-Geocoding

This operator co-registers two S-1 SLC split products (reference and secondary) of the same sub-swath using the orbits of the two products and a Digital Elevation Model (DEM).

DEM Assisted Coregistration:

This operator co-registers two two or more products using the orbits of the products and a Digital Elevation Model (DEM).

Furthermore, on the forum:

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

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 a…

However, I guess there must be some kind of difference since the former can input only SLC products whereas the latter can use GRD images. What piece am I missing?