NAME

       i.gensig  - Generates statistics for i.maxlik from raster map.

KEYWORDS

       imagery, classification, supervised classification, Maximum Likelihood Classification, MLC, signatures

SYNOPSIS

       i.gensig
       i.gensig --help
       i.gensig  trainingmap=name  group=name subgroup=name signaturefile=name  [--help]  [--verbose]  [--quiet]
       [--ui]

   Flags:
       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       trainingmap=name [required]
           Ground truth training map

       group=name [required]
           Name of input imagery group

       subgroup=name [required]
           Name of input imagery subgroup

       signaturefile=name [required]
           Name for output file containing result signatures

DESCRIPTION

       i.gensig is a non-interactive method for generating input into i.maxlik.  It can be  used  as  the  first
       pass  in  the  GRASS  two-pass classification process (instead of i.cluster or g.gui.iclass).  It reads a
       raster map layer, called the training map, which has some of the pixels or  regions  already  classified.
       i.gensig will then extract spectral signatures from an image based on the classification of the pixels in
       the training map and make these signatures available to i.maxlik.

       The user would then execute the GRASS program i.maxlik to actually create the final classified map.

OPTIONS

   Parameters
       trainingmap=name
           ground truth training map

       This  map  must  be  prepared  by  the  user in advance using vector or raster digitizer. Of course other
       methods could be devised by the user for creating this training map - i.gensig makes no assumption  about
       the  origin  of  this map layer. It simply creates signatures for the classes defined in the training map
       for the image to be classified (the image is specified in other options - see below).  The  wxGUI  vector
       digitizer can be used for interactively creating the training map.

       group=name
           imagery group

       This  is  the name of the group that contains the band files which comprise the image to be analyzed. The
       i.group  command is used to construct groups of raster layers which comprise an image.

       subgroup=name
           subgroup containing image files

       This names the subgroup within the group that selects a subset of the bands to be analyzed.  The  i.group
       command is also used to prepare this subgroup.  The subgroup mechanism allows the user to select a subset
       of all the band files that form an image.

       signaturefile=name
           resultant signature file

       This is the resultant signature file (containing the means and covariance matrices) for each class in the
       training map that is associated with the band files in the subgroup select (see above).

INTERACTIVE MODE

       If  none  of  the arguments are specified on the command line, i.gensig will interactively prompt for the
       names of these maps and files.

       It should be noted that interactive mode here only means interactive prompting for maps  and  files.   It
       does not mean visualization of the signatures that result from the process.

NOTES

       The  structure  of  the  SIG  files  generated  by i.gensig is as follows (ASCII file, used internally by
       i.maxlik):
       Note: the line numbers are not present in the file but have been added here for explanation only:

       SIG file "lsat7_2000_gensig":
        1 #
        2 #water
        3 4186
        4 67.9508 48.7346 37.8915 15.3129 13.8473 12.0855
        5 1.74334
        6 0.439504 2.07267
        7 0.662523 1.63501 4.21189
        8 0.530339 2.40757 5.52857 22.433
        9 0.561184 2.30762 5.18846 20.5364 20.4926
       10 0.393218 1.2184 2.63628 9.61528 9.36025 5.85314

           •   Line 2: text label

           •   Line 3: number of points in class

           •   Line 4: mean values per band of the class

           •   Line 5-10: (semi)-matrix of band-band covariance

SEE ALSO

        g.gui.iclass, i.group, i.smap, r.info, r.univar, wxGUI vector digitizer

AUTHOR

       Michael Shapiro, U.S.Army Construction Engineering Research Laboratory

       Last changed: $Date: 2014-11-01 11:11:04 +0100 (Sat, 01 Nov 2014) $

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       © 2003-2016 GRASS Development Team, GRASS GIS 7.0.3 Reference Manual

GRASS 7.0.3                                                                                     i.gensig(1grass)