In this chapter the processing of step UNWRAP is described. This step is currently not implemented within the Doris software. To obtain the unwrapped interferogram, you should use another software, for example one of the routines of [8] which can be obtained by ftp at ftp.wiley.com/public/sci_tech_med/phase_unwrapping. These software should not be considered public domain, you ought to buy the book. The slant to height conversion and geocoding can only be done with an unwrapped interferogram.
Recently "snaphu" of Curtis Cheng was put in the public domain. It is recommended you install this software as standalone executable, and continue with Doris for geocoding afterwards. METHOD snaphu can be used from within Doris. But experience has to be gained how this software best performs.
Sometimes the coherence as computed by doris seems to contian NaNs (not-a-number). snaphu does not expect this and exits when this happens. In Matlab the created coherence file can be easily corrected with, e.g.,
q=freadbk('9192_6687.coh',2577,'float32');
idxx=isnan(q);
idx=where(idxx==1);
q(idx)=0.0001;
fwritebk(q,'coh_no_nan','float32');
If you use a standalone application to unwrap the interferogram, you might have to mimic the output as described below, so Doris can obtain the current filename and dimensions for the unwrapped interferogram from the interferogram result file.