The simulation of master amplitude is computed in three steps:
First, the DEM is radarcoded to the coordinate systems of the master acquisition. For each DEM point, the master coordinates and the look angle are computed and saved to temporary files. Both the master coordinates and look angle are real valued.
Second, the look angle and topographic heights are 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 http://www.cs.cmu.edu/~quake/triangle.html. The interpolated topographic height and look angle are then used to compute the local incidence angle for each point. Using the local incidence angle we obtain the synthetic amplitude by
The is applied to obtain positive numbers.
Finally, the obtained simulated amplitude per master pixel are saved to a file and used in the M_TIMING step to obtain absolute timing error of the master acquisition.