Hello ABraun,
I myself am also struggling with eliminating a phase ramp in my study area that occurred during unwrapping. This post of your is quite interesting, though I was unable to find any information as to what it might mean. By a “modeled surface” do you mean a more accurate DEM to be used during topographic phase removal or are you referring to a different operation altogether? Any information on this (links to papers included) would be greatly appreciated.
Thank you!