Newsgroups: sci.image.processing
From: ricky@drift.demon.co.uk (Rick Turner)
Path: cantaloupe.srv.cs.cmu.edu!das-news2.harvard.edu!news2.near.net!news.mathworks.com!news.alpha.net!uwm.edu!vixen.cso.uiuc.edu!howland.reston.ans.net!pipex!peernews.demon.co.uk!drift.demon.co.uk!ricky
Subject: Re: NDVI?
References: <3gkc7j$d96@data.interserv.net>
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Date: Tue, 31 Jan 1995 20:04:16 +0000
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In article <3gkc7j$d96@data.interserv.net> adragoni@interserv.com  writes:

> I need information on whad NDVI is and what does it really represent.  All
>  information will be greatly
> appreciated.
>
> Alexis L. Dragoni
> San Juan, Puerto Rico
> adragoni@interserv.com
>
>

NDVI = normalised difference vegetation index.

It's a technique for measuring vegetation state (ie, health) from
Landsat MSS images. You get it from the following formula:

  NDVI = (near_IR - red)   =  (band 7 - band 5)
         ---------------      -----------------
         (near_IR + red)      (band 7 + band 5)

I have seen band 6 used instead of band 7.

Note that NDVI is only one of a whole bunch of measures designed to
do similar things. They measure either reflectance or emittance of
targets in some particular wavelength region.

All of them suffer from one problem or another - if I recall correctly
the problem with NDVI is that it is sensitive to soil darkening in
addition to vegetation changes, so rainfall (etc) can skew the readings.

--
Rick Turner
