Note that for the optimal results, i.e. to avoid an aliasing of spectras, the images first have to be oversampled by a factor two before multiplication for an optimal result. See sections on 'OVERSAMPLE' card.
For a more modular approach in the new method it is not advisable to subtract the reference phase in this step. If you do want to subtract the reference phase here, then make sure you first run Doris to run comprefpha, and then make a second run for step interfero.
After generation of the complex interferogram, the reference phase can be computed by the new module comprefpha and subtracted by the new module subtrrefpha. (Also a reference height model can be computed and subtracted in future modules.)
Figure 23.1 shows an example of a complex interferogram. Only the phase is shown here. We processed orbits 21066 and 1393 of frame 2781 (Italy), acquired at 26th and 27th July 1995 respectively (ERS1,2 Tandem mission). The parallel baseline is about 35 meters, which implies a height ambiguity of about 270 meters. Clearly a large trend caused by the 'flat earth' is present, but also some topographic features can be seen. In the frame the elavation ranges from zero to 1400 meters. (The original SLC images were cut out to 20000 lines by 4000 pixels, The interferogram is multiooked by factors 10 in azimuth and 2 in range, which yields a dimension of 1475 lines by 1997 pixels.)
 |