The frequency shift between the master and slave range data spectra equals

Where:

, is the local terrain
slope w.r.t. the ellipsoid, is the speed of light, is the
local incidence angle (!), is the radar wavelength, is
the slant range ground to master. The approximation is used in Doris.
Of course, the sign of
, or
is important to
filter the correct side of the spectra. Note that

(V2) |

The local incidence angle is computed with the dot product of vectors P, and P-M. See also [5].

The algorithm in Doris works as

- While there is a line in the overlap, get next line for master and slave.
- Get block of FFT_LENGTH pixels.
- Compute viewing angle, perpendicular baseline, delta theta for middle pixel of block.
- Compute frequency shift by equation 22.1, and compose filter of rect and hamming.
- Filter master and slave.
- Write block back (for last block only partially).