i.gensig: explain SIG file structure

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@56646 15284696-431f-4ddb-bdfa-cd5b030d7da7

imagery/i.gensig/i.gensig.html

@@ -14,26 +14,20 @@ has some of the pixels or regions already classified.
 <em>i.gensig</em> 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
-
 <em><a href="i.maxlik.html">i.maxlik</a></em>.
 
-
 <p>
 The user would then execute the GRASS program 
 <em><a href="i.maxlik.html">i.maxlik</a></em>
 to actually create the final classified map.
 
-
 <h2>OPTIONS</h2>
 
 <h3>Parameters</h3>
 
 <dl>
-
 <dt><b>trainingmap=</b><em>name</em>
-
 <dd>ground truth training map
-
 <p>
 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
@@ -43,9 +37,7 @@ the classes defined in the training map for the image to be classified
 (the image is specified in other options - see below).
 
 <dt><b>group=</b><em>name</em> 
-
 <dd>imagery group
-
 <p>
 This is the name of the group that contains the band files
 which comprise the image to be analyzed. The <em>
@@ -53,12 +45,10 @@ which comprise the image to be analyzed. The <em>
 used to construct groups of raster layers which comprise an
 image.
 
-
 <p>
 <dt><A NAME="subgroup"></a><b>subgroup=</b><em>name</em>
 
 <dd>subgroup containing image files
-
 <p>
 This names the subgroup within the group that selects a
 subset of the bands to be analyzed. The <em>
@@ -69,15 +59,12 @@ that form an image.
 
 
 <dt><b>signaturefile=</b><em>name</em> 
-
 <dd>resultant signature file
-
 <p>
 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 <a href="#subgroup">above</a>).
-
 </dl>
 
 <h2>INTERACTIVE MODE</h2>
@@ -86,31 +73,53 @@ If none of the arguments are specified on the command line,
 <em>i.gensig</em>
 will interactively prompt for the names of these maps and files.
 
-
 <p>
 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.
 
+<h2>NOTES</h2>
+
+The structure of the SIG files generated by <em>i.gensig</em> is
+as follows (ASCII file, used internally by <em>i.maxlik</em>):
+<br>
+<i>Note: the line numbers are not present in the file but have been
+added here for explanation only</i>:
+<p>
+SIG file "lsat7_2000_gensig":
+<div class="code"><pre>
+ 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 
+</pre></div>
+<ul>
+<li> Line 2: text label
+<li> Line 3: number of points in class
+<li> Line 4: mean values per band of the class
+<li> Line 5-10: (semi)-matrix of band-band covariance
+</ul>
 
 <h2>SEE ALSO</h2>
 
 <em><a href="i.group.html">i.group</a></em>
 for creating groups and subgroups.
-
 <p>
 <em><a href="wxGUI.vdigit.html">wxGUI vector digitizer</a></em>
 and
 <em><a href="r.digit.html">r.digit</a></em>
 for interactively  creating the training map.
-
 <p>
 <em><a href="i.cluster.html">i.cluster</a></em>
 for unsupervised clustering as an alternative to 
 <em>i.gensig</em> to create signatures.
-
-
 <p>
 <em><a href="g.gui.iclass.html">g.gui.iclass</a></em>
 for a graphic/interactive as an alternative to