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NAME

i.vi - Calculates different types of vegetation indices.
Uses red and nir bands mostly, and some indices require additional bands.

KEYWORDS

imagery, vegetation index, biophysical parameters

SYNOPSIS

i.vi
i.vi help
i.vi viname=string red=name [nir=name] [green=name] [blue=name] [chan5=name] [chan7=name] output=name [--overwrite] [--verbose] [--quiet]

Flags:

--overwrite
Allow output files to overwrite existing files
--verbose
Verbose module output
--quiet
Quiet module output

Parameters:

viname=string
Name of vegetation index
red=name
Name of the red channel surface reflectance map
Range: [0.0;1.0]
nir=name
Name of the nir channel surface reflectance map
Range: [0.0;1.0]
green=name
Name of the green channel surface reflectance map
Range: [0.0;1.0]
blue=name
Name of the blue channel surface reflectance map
Range: [0.0;1.0]
chan5=name
Name of the chan5 channel surface reflectance map
Range: [0.0;1.0]
chan7=name
Name of the chan7 channel surface reflectance map
Range: [0.0;1.0]
output=name
Name for output raster map

DESCRIPTION

i.vi calculates vegetation indices based on biophysical parameters.
ARVI: Atmospheric Resistant Vegetation Index 
ARVI is resistant to atmospheric effects (in comparison to 
the NDVI) and is accomplished by a self correcting process 
for the atmospheric effect in the red channel, using the 
difference in the radiance between the blue and the red 
channels.(Kaufman and Tanre 1996).
ARVI = (nirchan - (2.0*redchan - bluechan)) / 
( nirchan + (2.0*redchan - bluechan))
arvi( redchan, nirchan, bluechan )
DVI: Difference Vegetation Index
DVI = ( nirchan - redchan )
dvi( redchan, nirchan )
EVI: Enhanced Vegetation Index
Huete A.R., Liu H.Q., Batchily K., vanLeeuwen W. (1997). 
A comparison of vegetation indices global set of TM images for 
EOS-MODIS. Remote Sensing of Environment, 59:440-451.
EVI = 2.5 * ( nirchan - redchan ) / 
( nirchan + 6.0 * redchan - 7.5 * bluechan + 1.0 )
evi( bluechan, redchan, nirchan )
GARI: green atmospherically resistant vegetation index
GARI = ( nirchan - (greenchan-(bluechan - redchan))) / 
( nirchan- (greenchan-(bluechan - redchan)))
gari( redchan, nirchan, bluechan, greenchan )
GEMI: Global Environmental Monitoring Index
GEMI = (( (2*((nirchan * nirchan)-(redchan * redchan))+
1.5*nirchan+0.5*redchan) / (nirchan + redchan + 0.5)) * 
(1 - 0.25 * (2*((nirchan * nirchan)-(redchan * redchan))
+1.5*nirchan+0.5*redchan) /(nirchan + redchan + 0.5)))-
( (redchan - 0.125) / (1 - redchan))
gemi( redchan, nirchan )
GVI: Green Vegetation Index
GVI = ( -0.2848 * bluechan - 0.2435 * greenchan - 
0.5436 * redchan + 0.7243 * nirchan + 0.0840 * chan5chan-
0.1800 * chan7chan)
gvi( bluechan, greenchan, redchan, nirchan, chan5chan, chan7chan)
IPVI: Infrared Percentage Vegetation Index 
IPVI = nirchan/(nirchan+redchan)
ipvi( redchan, nirchan )
MSAVI2: second Modified Soil Adjusted Vegetation Index
MSAVI2 = (1/2)*(2(NIR+1)-sqrt((2*NIR+1)^2-8(NIR-red)))
msavi2( redchan, nirchan )
MSAVI: Modified Soil Adjusted Vegetation Index
MSAVI = s(NIR-s*red-a) / (a*NIR+red-a*s+X*(1+s*s))	
where a is the soil line intercept, s is the
soil line slope, and X 	is an adjustment factor
which is set to minimize soil noise (0.08 in 
original papers).			
msavi( redchan, nirchan )
NDVI: Normalized Difference Vegetation Index 
Data Type Band Numbers ([IR, Red]) 
TM Bands= [4,3] 
MSS Bands = [7, 5] 
AVHRR Bands = [2, 1] 
SPOT XS Bands = [3, 2] 
AVIRIS Bands = [51, 29] 


(AVHRR) NDVI = (channel 2 - channel 1) / (channel 2 + channel 1)
PVI: Perpendicular Vegetation Index
PVI = sin(a)NIR-cos(a)red 
for a isovegetation lines (lines of equal vegetation)
would all be parallel to the soil line therefore a=1
pvi( redchan, nirchan )
SAVI: Soil Adjusted Vegetation Index
SAVI = ((1.0+0.5)*(nirchan - redchan)) / (nirchan + redchan +0.5)
savi( redchan, nirchan )
SR: Simple Vegetation ratio
SR = (nirchan/redchan)
sr( redchan, nirchan )
VARI: Visible Atmospherically Resistant Index
VARI = (green - red ) / (green + red - blue)
it was designed to introduce an atmospheric self-correction 
Gitelson A.A., Kaufman Y.J., Stark R., Rundquist D., 2002.
Novel algorithms for estimation of vegetation fraction 
Remote Sensing of Environment (80), pp76-87. 
WDVI: Weighted Difference Vegetation Index
WDVI = nirchan - a * redchan
if(soil_weight_line == None):
a = 1.0 #slope of soil line
wdvi( redchan, nirchan, soil_line_weight )

NOTES

Originally from kepler.gps.caltech.edu
A FAQ on Vegetation in Remote Sensing 
Written by Terrill W. Ray
	   Div. of Geological and Planetary Sciences
	   California Institute of Technology
email: terrill@mars1.gps.caltech.edu
Snail Mail:  Terrill Ray
	     Division of Geological and Planetary Sciences
	     Caltech
	     Mail Code 170-25
	     Pasadena, CA  91125

SEE ALSO

i.albedo

AUTHORS

Baburao Kamble, Asian Institute of Technology, Thailand
Yann Chemin, Asian Institute of Technology, Thailand

Last changed: $Date: 2006/10/09 21:30:42 $


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