snaphu_man1.html

phase unwrapping algorithm for SAR interferometry

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Assemble the tile-mode temporary files in the specified
directory. Most configuration options (from the command line
and any configuration files) must be specified. This option
is useful if the user wishes to modify tile-assembly
parameters without unwrapping the individual tiles over
again.</td></table><p>

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<b>--copyright, --info</b></td></table><p>

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Print the software copyright notice and bug report info,
then exit.</td></table><p>

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<b>--costinfile</b> <i>costfile</i></td></table><p>

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Read statistical cost arrays from file <i>costfile</i>. This
file should be in the format written by the
<b>--costoutfile</b> option. The cost file does not control
whether <b>snaphu</b> runs in topography, deformation, or
smooth-solution mode; the latter two must be specified
explicitly even if <i>costfile</i> was generated while
running in those modes.</td></table><p>

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<b>--costoutfile</b> <i>costfile</i></td></table><p>

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Write statistical cost arrays to file <i>costfile</i>. This
option can be used with the <b>--costinfile</b> option to
save the time of generating statistical costs if the same
costs are used multiple times.</td></table><p>

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<b>--debug, --dumpall</b></td></table><p>

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Dump all sorts of intermediate arrays to files.</td></table><p>

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<b>--mst</b></td></table><p>

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Use a minimum spanning tree (MST) algorithm for the
initialization. This is the default.</td></table><p>

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<b>--mcf</b></td></table><p>

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Use a minimum cost flow (MCF) algorithm for the
initialization. The cs2 solver by Goldberg and Cherkassky is
used. The modified network-simplex solver in L1 mode may
give different results than the cs2 solver, though in
principle both should be L1 optimal.</td></table><p>

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<b>--nproc</b> <i>n</i></td></table><p>

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Use <i>n</i> parallel processes when in tile mode. The
program forks a new process for each tile so that tiles can
be unwrapped in parallel; at most <i>n</i> processes will
run concurrently. Forking is done before data is read. The
standard output streams of child processes are directed to
log files in the temporary tile directory.</td></table><p>

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<b>--piece</b> <i>firstrow firstcol nrow
ncol</i></td></table><p>

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Read and unwrap only a subset or part of the input
interferogram. The read piece is the <i>nrow</i> by
<i>ncol</i> rectangle whose upper left corner is the pixel
at row <i>firstrow</i> and column <i>firstcol</i> (indexed
from 1). All input files (such as amplitude, coherence,
etc.) are assumed to be the same size as the input phase
file. All output files are <i>nrow</i> by
<i>ncol</i>.</td></table><p>

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<b>--tile</b> <i>ntilerow ntilecol rowovrlp
colovrlp</i></td></table><p>

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Unwrap the interferogram in tile mode. The interferogram is
partitioned into <i>ntilerow</i> by <i>ntilecol</i> tiles,
each of which is unwrapped independently. Tiles overlap by
<i>rowovrlp</i> and <i>colovrlp</i> pixels in the row and
column directions. The tiles are then segmented into
reliable regions based on the cost functions, and the
regions are reassembled. The program creates a subdirectory
for temporary files in the directory of the eventual output
file. This option is currently enabled only for statistical
cost functions.</td></table><p>
<a name="FILE FORMATS"></a>
<h2>FILE FORMATS</h2>

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The formats of input files may be specified in a
configuration file. All of these formats are composed of
raster, single-precision (float, real*4, or complex*8)
floating-point data types in the platform's native byte
order. Data are read line by line (across then down).
Regardless of the file format, all input data arrays should
have the same number of samples in width and depth and
should be coregistered to one another. Note that weight
files and cost files have their own formats. The allowable
formats for other data files are described
below.</td></table><p>

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COMPLEX_DATA</td></table><p>

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Alternating floats correspond to the real (in-phase) and
imaginary (quadrature) components of complex data samples.
The specified line length should be the number of complex
samples (pairs of real and imaginary samples) per
line.</td></table><p>

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ALT_LINE_DATA</td></table><p>

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Alternating lines (rows) of data correspond to lines of
purely real data from two separate arrays. The first array
is often the magnitude of the interferogram, and the second
may be unwrapped phase, coherence, etc. This is also
sometimes called <b>hgt</b> or line-interleaved
format.</td></table><p>

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ALT_SAMPLE_DATA</td></table><p>

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Alternating samples correspond to purely real samples from
two separate arrays. This format is sometimes used for the
amplitudes of the two SAR images.</td></table><p>

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FLOAT_DATA</td></table><p>

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The file contains data for only one channel or array, and
the data are purely real.</td></table><p>
<a name="EXAMPLES"></a>
<h2>EXAMPLES</h2>

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Unwrap a wrapped topographic interferogram called
``wrappedfile'' whose line length is 1024 complex samples
(output will be written to a file whose name is compiled
into the program):</td></table><p>

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<pre>     snaphu wrappedfile 1024
</pre>Unwrap the same file as above, but use brightness information from the file ``ampfile,'' set the perpendicular baseline to -165 m at midswath, and place the output in a file called ``unwrappedfile'' (coherence data are generated automatically if ``wrappedfile'' contains complex data and ``ampfile'' contains amplitude data from both SAR images):</td></table><p>

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<pre>     snaphu wrappedfile 1024 -a ampfile \
          -b -165 -o unwrappedfile
</pre>Unwrap the interferogram as above, but read correlation information from the file ``corrfile'' instead of generating it from the interferogram and amplitude data:</td></table><p>

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<pre>     snaphu wrappedfile 1024 -a ampfile -c corrfile \
          -b -165 -o unwrappedfile
</pre>The following is equivalent to the previous example, but input parameters are read from a configuration file, and verbose output is displayed:</td></table><p>

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<pre>     cat &gt; configfile
     # This is a comment line which will be ignored
     AMPFILE      ampfile
     CORRFILE     corrfile
     BPERP        -165
     OUTFILE      unwrappedfile
     &lt;Ctrl-D&gt;

     snaphu -v -f configfile wrappedfile 1024
</pre>Unwrap the same interferogram, but use only the MST initialization (with scalar statistical weights) and write the output to ``mstfile'':</td></table><p>