NAME

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

KEYWORDS

       imagery, classification, supervised, MLC

SYNOPSIS

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

   Parameters:
       trainingmap=name
           Ground truth training map

       group=name
           Name of input imagery group

       subgroup=name
           Name of input imagery subgroup

       signaturefile=string
           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 i.class).  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. Programs like v.digit or r.digit can be used to  define
       representative  areas  of the classes the user defines to be in the image.  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).

       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

       i.group for creating groups and subgroups.

       v.digit and r.digit for interactively  creating the training map.

       i.cluster for unsupervised clustering as an alternative to i.gensig to create signatures.

       i.class for a graphic/interactive as an alternative to i.gensig to create signatures.

AUTHOR

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

       Last changed: $Date: 2013-06-09 14:37:33 +0200 (Sun, 09 Jun 2013) $

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       © 2003-2013 GRASS Development Team

GRASS 6.4.3                                                                                     i.gensig(1grass)