ABraun
June 15, 2020, 3:11pm
31
The answer is given by @eyeinsky here: Gamma0 only corrects for the global incidence angle (ellipsoid) while Gamma0 producced by Terrain Flattening corrects for the local illuminated area (topography):
Concerning gamma nought, one should distinguish between the variant that only compensates for an ellipsoidal incident angle, versus an approach where the local terrain facets are projected into the gamma nought convention (perpendicular to slant range) and integrated throughout a whole DEM to give a “terrain-flattened” result. Beta nought is not compensated even for ellipsoidal incident angle - it reflects the “raw” measurement at the radar, and is extremely ill-suited to land-cover analysis.
It is explained here why we need Beta0 first: Radiometric & Geometric Correction Workflow - #71 by ABraun