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.

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

SOURCE CODE

       Available at: i.gensig source code (history)

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual