i.vi manual: NDVI example added

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@58620 15284696-431f-4ddb-bdfa-cd5b030d7da7

imagery/i.vi/i.vi.html

@@ -247,6 +247,17 @@ if(soil_weight_line == None):
 wdvi( redchan, nirchan, soil_line_weight )
 </pre></div>
 
+<h2>EXAMPLE</h2>
+This example uses a LANDSAT TM5 scene included in the North Carolina sample
+dataset. 
+
+<!-- todo: check if i.landsat.toar use is needed for NC data -->
+<div class="code"><pre>
+g.region rast=lsat5_1987_30 -p
+i.vi red=lsat5_1987_30 viname=ndvi output=lsat5_1987.ndvi nir=lsat5_1987_40
+r.colors lsat5_1987.ndvi color=ndvi
+</pre></div>
+
 <h2>NOTES</h2>
 
 Originally from kepler.gps.caltech.edu: