[GRASS-dev] i.fusion.hpf addon: observing strong range change

[Veronica Andreo]

Hi,

I had the same problem last time I used i.fusion.hpf for pansharpening a
SPOT image (6m to 1.5m). Question is in my view if the resulting values
mean anything (i.e., they can be used for estimation of spectral indices)
or it is just for visual purposes? Sorry for my ignorance, but I haven't
found a clear-cut answer to this...

On the other hand, i.pansharpen does include a re-scaling step, but
whatever bit depth is passed as input it will be re-scaled to 8-bit. If the
input data is >8-bit, it is a bit of a loss of radiometric resolution (if
the resulting values can be used for indices estimation)...

I'd appreciate your insights

Cheers,
Vero





El lun., 28 oct. 2019 a las 17:40, Markus Neteler (<neteler at osgeo.org>)
escribió:

> On Mon, Oct 28, 2019 at 4:44 PM Moritz Lennert
> <mlennert at club.worldonline.be> wrote:
> > On 28/10/19 12:33, Markus Neteler wrote:
> > > On Mon, Oct 28, 2019 at 10:46 AM Moritz Lennert
> > > <mlennert at club.worldonline.be> wrote:
> > >> On 27/10/19 18:52, Markus Neteler wrote:
> > >>> Hi,
> > >>>
> > >>> I am using i.fusion.hpf on Worldview-2 data and see that the
> resulting
> > >>> range is completely different:
> > >>>
> > >>> # orig
> > >>> r.info -r wv2_17OCT08182034_M2AS_058891334010_01_P001.5
> > >>> min=0
> > >>> max=1509
> > >>>
> > >>> # HPF
> > >>> r.info -r wv2_17OCT08182034_M2AS_058891334010_01_P001.5.hpf
> > >>> min=-1045.79783524995
> > >>> max=3416.06793724612
> > >>
> > >> Just guessing here, but did you try the -c flag ?
> > >
> > > Now yes:
> > >
> > > i.fusion.hpf pan=$PAN msx=$(g.list raster pattern="$COLORPREFIX.?"
> > > sep=comma) -c --o
> > >
> > > # band 8
> > > r.info -r wv2_17OCT08182034_M2AS_058891334010_01_P001.8
> > > min=0
> > > max=1605
> > >
> > > r.info -r wv2_17OCT08182034_M2AS_058891334010_01_P001.8.hpf
> > > min=-1163.98434592277
> > > max=3879.99538075697
> > >
> > > So, -c doesn't seem to have any effect here.
> > >
> >
> > Sorry, wrong flag, should have been -l ("Linearly match histogram of
> > Pan-sharpened output to Multi-Spectral input")
>
> This comes with -l:
>
> r.info -r wv2_17OCT08182034_M2AS_058891334010_01_P001.8.hpf
> min=-932.700879728634
> max=3456.94617091076
>
> > And if you rescale the output manually to the input value range, do you
> > still see a good fusion result ? If yes, then this could be added as a
> > last step to the module.
>
> In lack of time I cannot test that right now.
>
> Nikos has a subset of my data, maybe he's able to check with that.
>
> Markus
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