[GRASS-user] pansharp fusion of ikonos image

[Brad Douglas]

Interesting method.  I've never tried that one, but it makes complete
sense.  I may have to write a module to "rewind" i.pca (added to bottom
of nearly infinite queue :-).

Another method of pan-sharpening:
- Run RGB through i.rgb.his
- Replace the intensity channel with the pan image
- Change resolution to the pan image
- Revert to RGB with i.his.rgb.

This method generally preserves spectral characteristics.

On Mon, 2007-02-26 at 13:02 -0800, Jonathan Greenberg wrote:
> Just as a heads up, most pansharpening algorithms introduce false spectral
> information into the mix -- you might want to look into principle components
> pansharpening algorithms, which tend to preserve the spectral values better
> than the other commonly used ones...
> 
> http://scholar.google.com/scholar?hl=en&lr=&q=welch+merging+spot&btnG=Search
> 
> The first hit is the paper that describes this (Welch and Ehlers, 1987)
> 
> The basic concept is you rotate a resampled "high resolution" multispectral
> data (I think a nearest neighbor resample to match the high res resolution
> is sufficient) into PCA space, the first PCA axis tends to be the albedo
> band (which is the assumption for this analysis).  The high resolution pan
> band is then substituted in to the PCA stack, replacing the first PCA axis
> band, and then rotated back into spectral space.
> 
> I used this pansharpened data as the basis for several published papers
> using IKONOS imagery, and it works very nicely (I used ENVI's implementation
> of the algorithm)
> 
> --j
> 
> 
> On 2/26/07 12:48 PM, "Markus Neteler" <neteler at itc.it> wrote:
> 
> > 
> > Hi Massimo,
> > 
> > please have a look at
> > http://grass.itc.it/grass63/manuals/html63_user/imageryintro.html
> > -> Image fusion
> > 
> > or 
> > g.manual imageryintro
> > -> Image fusion
> > 
> > I agree that it is minimalistic, please suggest how to improve the text
> > (text snippets welcome!).
> > 
> > So, yes, you have at least two possibilites besides r.mapcalc.
> > 
> > Markus
> > 
> > 
> > Massimo Di Stefano wrote:
> >> 
> >> Hi,
> >> 
> >> have you any suggestion on how can i do a ikonos "pansharp fusion"
> >> using grass ?
> >> there isn't a command that already done this things,
> >> is possible to use an r.mapcalc expression to do it ? have you
> >> experience about ?
> >> thanks for any help!
> >> Massimo.


-- 
Brad Douglas <rez touchofmadness com>                    KB8UYR/6
Address: 37.493,-121.924 / WGS84    National Map Corps #TNMC-3785