General considerations and conventions

In this section some important definitions are described that are used in the Doris software. This will clarify the terminlogy used. The general set up of the input file and output files is described as well.

After compilation with the Makefile, the executable is named: "doris". In this document therefor this name is used to refer to the executable. The command line options are:

• doris -ver
  return version number.
• doris -h
  return help (system call to shell script named helpdoris).
• doris [file]
  run, use input in ''file'' (default: ''inputoptionsfile''.

It is advised also to compile an executable ''doris.debug'' (with the Makefile). This version is somewhat slower and more verbose, but it can be used if something seems to go wrong with the normal executable, and it is not clear what. See also Annex B. We advice to use the utility scripts to generate input files and to run the processor.

Conventions are:

• We use the term lines to refer to the azimuth direction (slow time), and pixels for the range direction (fast time). (A pixel might also refer to an element, which will be clear from the context.) In the source code we frequently use the term azimuth buffers and range blocks.
• Our convention is to use first lines, second pixels, e.g., for the order of input arguments. The line direction (azimuth) corresponds to the vertical (y). The pixel direction (range) corresponds to the horizontal (x). Note that other software may use x before y.
• The first line (pixel) of an image is indexed as 1 (this may be a bit unusual). (In the software, the first index of an image (in a matrix) is equal to 0. To index a matrix, use MAT(y,x), i.e., as in linear algebra, Matlab, etc.)
• The name, format, and dimensions of the current master/slave/interferogram are stored in information structs that are filled by reading the corresponding result files. The files do not have a header.
• Generally all coordinates are in the master (radar) coordinate system. The first and last line are given, as well as multilook factors for both directions. If for example an interferogram is multilooked at the generation with a certain factor and later on again at the subtraction of the reference phase, then the first line is still the same, see Figure 1.3.
• In our view, the output files can only contain the results of one algorithm per step. So it is not possible to re-run a step (for example with another algorithm) without deleting the previous result. New users may be confused by this approach, but Doris should give an appropriate error message if it is attempted to run a step twice.
• Temporary files are created during the processing. Their names always start with "scratch". If such files are not removed by Doris, for example after an error in the processing, they can be savely removed by a rm command.

Figure 1.3: Principle of multilooking.

In the logfile additional information is written that is not sent to standard out or the result files, such as statistical information on a least squares estimate. (For example, we always inspect the correlation value for step COARSE_CORR, and the error between model and observations for reference phase computations in the log file.)