The DEM reference phase is computed in two steps:
First, the DEM is radarcoded to the coordinate systems of the master image. Per DEM point the master coordinate (real valued) and the computed reference phase is saved to a file.
Second, the reference phase is interpolated to the integer grid of master
coordinates. A linear interpolation based on a Delaunay triangulation
is used. The software package Triangle for the Delaunay
triangulation is kindly made available by Jonathan Shewchuk
[16,17], see also