Radiometric Terrain Falttening: Additional Inputs

What are the additional user inputs involved in case of Radiometric Terrain Flattening?
-DEM No Data Value
-DEM Resampling Method
-External DEM Apply EGM
-Additional Overlap Percentage
-Oversampling Multiple

Did you see that these are documented in the help?

DEM Resampling Method, Additional Overlap Percentage, Oversampling Multiple


External DEM Apply EGM
EGM stands for Earth Gravitational Model ( Can be checked for more precise estimation of the earth’s surface.