[GRASS-dev] [GRASS GIS] #2098: i.vi gari wrong formula?

[Yann Chemin]

>From the code:

result = (nirchan - (greenchan - (bluechan - redchan)))/(nirchan -
(greenchan - (bluechan + redchan)));



On 10 October 2013 00:07, GRASS GIS <trac at osgeo.org> wrote:

> #2098: i.vi gari wrong formula?
>
> -----------------------+----------------------------------------------------
>  Reporter:  kristinah  |       Owner:  grass-dev@…
>      Type:  defect     |      Status:  new
>  Priority:  normal     |   Milestone:  6.4.4
> Component:  Default    |     Version:  unspecified
>  Keywords:             |    Platform:  Unspecified
>       Cpu:  All        |
>
> -----------------------+----------------------------------------------------
>  The formula for GARI in the manual
>  (http://grass.osgeo.org/grass70/manuals/i.vi.html) seems to be wrong. As
>  it is now, the result would always be 1.
>
>  It is
>  "
>  GARI = ( nirchan - (greenchan-(bluechan - redchan))) /
>  ( nirchan- (greenchan-(bluechan - redchan)))
>  "
>
>  It should be (e.g. according to
>  http://www.indexdatabase.de/db/i-single.php?id=363)
>  "
>  GARI = ( nirchan - (greenchan-(bluechan - redchan))) /
>  ( nirchan- (greenchan+(bluechan - redchan)))
>  "
>
>  As the formula in the manual seems to be taken from code, the code might
>  be wrong as well. I did not test the function, only read the manual
>  online.
>
> --
> Ticket URL: <https://trac.osgeo.org/grass/ticket/2098>
> GRASS GIS <http://grass.osgeo.org>
>
> _______________________________________________
> grass-dev mailing list
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