i.gensig(1grass) GRASS GIS User's Manual i.gensig(1grass)
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.max-
lik. It can be used as the first pass in the GRASS two-pass classifi-
cation 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 cre-
ate 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 com-
prise the image to be analyzed. The i.group command is used to con-
struct 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 covari-
ance 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 digi-
tizer
AUTHOR
Michael Shapiro, U.S.Army Construction Engineering Research Laboratory
SOURCE CODE
Available at: i.gensig source code (history)
Accessed: unknown
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GRASS 7.8.7 i.gensig(1grass)
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