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    [--overwrite]   [--help]
       [--verbose]  [--quiet]  [--ui]

   Flags:
       --overwrite
           Allow output files to overwrite existing files

       --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.

       This  module  generates  signature  files  of  type  "sig".  Use  module i.signatures to manage generated
       signature files.

       All raster maps used to generate signature file can  have  semantic  label  set.  Use  r.support  to  set
       semantic labels of each member of the imagery group.  Signatures generated for one scene are suitable for
       classification of other scenes as long as they consist of same raster bands (semantic labels match).

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). Resultant
       singature file can be used with any other imagery group as long as semantic labels match.

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 1
        2 #
        3 Semantic_label1
        4 #water
        5 4186
        6 67.9508 48.7346 37.8915 15.3129 13.8473 12.0855
        7 1.74334
        8 0.439504 2.07267
        9 0.662523 1.63501 4.21189
       10 0.530339 2.40757 5.52857 22.433
       11 0.561184 2.30762 5.18846 20.5364 20.4926
       12 0.393218 1.2184 2.63628 9.61528 9.36025 5.85314

           •   Line 1: version number (currently always 1)

           •   Line 2: text label

           •   Line 3: Space separated list of semantic labels

           •   Line 4: text label of class

           •   Line 5: number of points in class

           •   Line 6: mean values per band of the class

           •   Line 7-12: (semi)-matrix of band-band covariance

SEE ALSO

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

AUTHORS

       Michael Shapiro, U.S.Army Construction Engineering Research Laboratory
       Semantic label support: Maris Nartiss, University of Latvia

SOURCE CODE

       Available at: i.gensig source code (history)

       Accessed: Friday Apr 04 01:20:54 2025

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       © 2003-2025 GRASS Development Team, GRASS GIS 8.4.1 Reference Manual

GRASS 8.4.1                                                                                     i.gensig(1grass)