[GRASS-SVN] r58389 - grass/trunk/imagery/i.vi

[svn_grass at osgeo.org]

Author: lucadelu
Date: 2013-12-05 00:14:46 -0800 (Thu, 05 Dec 2013)
New Revision: 58389

Modified:
   grass/trunk/imagery/i.vi/gari.c
   grass/trunk/imagery/i.vi/i.vi.html
Log:
update GARI formula

Modified: grass/trunk/imagery/i.vi/gari.c
===================================================================
--- grass/trunk/imagery/i.vi/gari.c	2013-12-04 23:28:46 UTC (rev 58388)
+++ grass/trunk/imagery/i.vi/gari.c	2013-12-05 08:14:46 UTC (rev 58389)
@@ -7,7 +7,7 @@
 {
     double result;
     {
-        result = (nirchan - (greenchan - (bluechan - redchan)))/(nirchan - (greenchan + (bluechan - redchan)));
+        result = (nirchan - (greenchan - (bluechan - redchan)))/(nirchan + (greenchan - (bluechan - redchan)));
     }
     return result;
 }

Modified: grass/trunk/imagery/i.vi/i.vi.html
===================================================================
--- grass/trunk/imagery/i.vi/i.vi.html	2013-12-04 23:28:46 UTC (rev 58388)
+++ grass/trunk/imagery/i.vi/i.vi.html	2013-12-05 08:14:46 UTC (rev 58389)
@@ -122,10 +122,16 @@
 
 <p>
 GARI: green atmospherically resistant vegetation index
+<p>
+The formula was actually defined:
+Gitelson, Anatoly A.; Kaufman, Yoram J.; Merzlyak, Mark N. (1996)
+Use of a green channel in remote sensing of global vegetation from EOS-
+MODIS, Remote Sensing of Environment 58 (3), 289-298.
+<a href="http://dx.doi.org/10.1016/s0034-4257(96)00072-7">doi:10.1016/s0034-4257(96)00072-7</a>
 
 <div class="code"><pre>
 GARI = ( nirchan - (greenchan - (bluechan - redchan))) / 
-( nirchan - (greenchan + (bluechan - redchan)))
+( nirchan + (greenchan - (bluechan - redchan)))
 gari( redchan, nirchan, bluechan, greenchan )
 </pre></div>