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.

       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: Mon Jun 13 15:10:47 2022

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       © 2003-2022 GRASS Development Team, GRASS GIS 8.2.0 Reference Manual