5
is a non-interactive method for generating input into
6
<EM><A HREF="i.maxlik.html">i.maxlik</A></EM>.
7
It can be used as the first pass in the GRASS two-pass
8
classification process (instead of
9
<EM><A HREF="i.cluster.html">i.cluster</A></EM>
11
<EM><A HREF="i.class.html">i.class</A></EM>).
13
It reads a raster map layer, called the training map, which
14
has some of the pixels or regions already classified.
15
<EM>i.gensig</EM> will then extract spectral signatures
16
from an image based on the classification of the pixels in
17
the training map and make these signatures available to
19
<EM><A HREF="i.maxlik.html">i.maxlik</A></EM>.
24
The user would then execute the GRASS program
25
<EM><A HREF="i.maxlik.html">i.maxlik</A></EM>
26
to actually create the final classified map.
35
<DT><B>trainingmap=</B><EM>name</EM>
37
<DD>ground truth training map
41
This map must be prepared by the user in advance. Programs like
42
<EM><A HREF="v.digit.html">v.digit</A></EM> or <EM>
43
<A HREF="r.digit.html">r.digit</A></EM> can be
44
used to define representative
45
areas of the classes the user defines to be in the image.
46
Of course other methods could be devised by the user for creating
47
this training map - <EM>i.gensig</EM> makes no assumption about the origin
48
of this map layer. It simply creates signatures for the classes defined
49
in the training map for the image to be classified (the image is
50
specified in other options - see below).
52
<DT><B>group=</B><EM>name</EM>
58
This is the name of the group that contains the band files
59
which comprise the image to be analyzed. The <EM>
60
<A HREF="i.group.html">i.group</A> </EM> command is
61
used to construct groups of raster layers which comprise an
67
<A NAME="subgroup"><DT><B>subgroup=</B><EM>name</EM></A>
69
<DD>subgroup containing image files
73
This names the subgroup within the group that selects a
74
subset of the bands to be analyzed. The <EM>
75
<A HREF="i.group.html">i.group</A> </EM> command is
76
also used to prepare this subgroup. The subgroup mechanism
77
allows the user to select a subset of all the band files
81
<DT><B>signaturefile=</B><EM>name</EM>
83
<DD>resultant signature file
87
This is the resultant signature file (containing the means
88
and covariance matrices) for each class in the training map
89
that is associated with the band files in the subgroup
90
select (see <A HREF="#subgroup">above</A>).
94
<H2>INTERACTIVE MODE</H2>
96
If none of the arguments are specified on the command line,
98
will interactively prompt for the names of these maps and files.
103
It should be noted that interactive mode here only means
104
interactive prompting for maps and files.
105
It does not mean visualization of the signatures that
106
result from the process.
111
<EM><A HREF="i.group.html">i.group</A></EM>
112
for creating groups and subgroups.
116
<EM><A HREF="v.digit.html">v.digit</A></EM>
118
<EM><A HREF="r.digit.html">r.digit</A></EM>
119
for interactively creating the training map.
123
<EM><A HREF="i.cluster.html">i.cluster</A></EM>
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for unsupervised clustering as an alternative to
125
<EM>i.gensig</EM> to create signatures.
130
<EM><A HREF="i.class.html">i.class</A></EM>
131
for a graphic/interactive as an alternative to
132
<EM>i.gensig</EM> to create signatures.
137
U.S.Army Construction Engineering Research Laboratory
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<p><i>Last changed: $Date: 2003-04-17 16:51:33 +0200 (Thu, 17 Apr 2003) $</i>