[mapserver-users] How reproduce a false color NDVI.

[Even Rouault]

Le mardi 03 mars 2015 00:34:49, aperi2007 a écrit :
> Hi Even,
> 
> I'll try to test the usage of the VRT format (I never use it before).

Andrea,

My point was that wile it could be potentially an interesting way of doing it, 
in the current state of things, you need to write a C function, link it with 
GDAL or MapServer, and call a register function, which likely makes it 
impractical for most people.

Even

> 
> Thx,
> Andrea.
> 
> Il 01/03/2015 10:35, Even Rouault ha scritto:
> > Le dimanche 01 mars 2015 10:17:34, Andrea Peri a écrit :
> >> Hi,
> >> we have a set of tiffs georef with 4th bands of color RGB and Infrared.
> >> We need to activate a wms with the color from the NDVI index
> >> 
> >> NDVI = Normalized Difference Vegetation Index
> >> 
> >>            NIR - RED
> >> 
> >> NDVI = -------------
> >> 
> >>            NIR + RED
> >> 
> >> Where NIR is the 4th band,
> >> RED s the 1th band.
> >> 
> >> We prefer dont' do a physical float raster, but retrieve this realtime
> >> from the original tiffs.
> >> 
> >> I try to reproduce this index NDVI using to a LUT table in MapServer,
> >> but without any success.
> >> There is some other solution to obtain this on mapserver.
> > 
> > Andrea,
> > 
> > It turns out that the same question was asked more than 10 years ago :
> > http://lists.osgeo.org/pipermail/mapserver-users/2004-July/053754.html
> > 
> > Since them, GDAL has the VRT format. With derived bands (described near
> > the end of http://gdal.org/gdal_vrttut.html), you could do that but that
> > requires writing a custom function in C, which isn't very convenient for
> > integration with MapServer. It would be nice to add the capability of
> > writing pixel functions in Python.
> > 
> > Even

-- 
Spatialys - Geospatial professional services
http://www.spatialys.com