Provided by: grass-doc_7.6.0-1_all bug


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


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


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

           Allow output files to overwrite existing files

           Print usage summary

           Verbose module output

           Quiet module output

           Force launching GUI dialog

       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


       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.


           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.

           imagery group

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

           subgroup containing image files

       This names the subgroup within the group  that  selects  a  subset  of  the  bands  to  be
       analyzed.  The   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.

           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).


       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.


       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


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


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

       Last changed: $Date: 2014-11-01 11:07:51 +0100 (Sat, 01 Nov 2014) $


       Available at: i.gensig source code (history)

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