[GRASS-user] Color equalization after patching/mosaicking the satellite data from multiple scenes

[anna zanchetta]

Hi Sajid and Nikos,

I'm also in the same situation, needing to patch (mosaic) several Landsat5
images from the 80s, different dates and different paths.
I wasn't considering radiometric corrections though, but the histogram
matching, and for this I've tried to use i.histo.match addon, which showed
for me some problems.
Therefore I'm considering to retouch the script of the addon, and I did
already contact the author (Luca Delucchi) for this and subsequently Markus
Neteler, who made me available the source for the theoretical basis behind
it - in Italian. If you have any suggestions or want to collaborate, please
let me know, it's not an easy time for me to invest in this new issue and
any help will be welcome.
If you prefer to continue this discussion off-list, that will be fine for
me.
Bye!

Anna




> Date: Sun, 1 Jan 2017 18:12:48 +0100
> From: Sajid Pareeth <spareeth at gmail.com>
> To: Nikos Alexandris <nik at nikosalexandris.net>
> Cc: GRASS user list <grass-user at lists.osgeo.org>
> Subject: Re: [GRASS-user] Color equalization after patching/mosaicking
>         the satellite data from multiple scenes
> Message-ID:
>         <CAO7vHBEQBFQXJj8jot6VwEyFQ-Y6EkRnv4At7U517MUp6kvv2g at mail.
> gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Hi Nikos,
>
> Thank you for the reply.
>
> some normalisation, before patching, is what "needs" to be done, I think.
> > Relative
> > normalisation here (either for images of different dates over the same
> > area, or neighbouring images of the same date).
> >
>
> Yes I also agree with that, I tried doing histogram matching before running
> r.patch, though I am not sure if it is right way. Any idea on how the
> change in values due to matching will affect further processing?
>
> >
> > I never finished implementing some very simple process as described in
> > user manual(s) for QuickBird2 imagery, if I remember well.
> >
> > I have a draft module which I named i.radio.balance. In short:  the
> > major difference between two scenes of the same area is the solar
> > geometry.  This difference can be minimized by correcting imagery for
> > Earth-sun distance and solar zenith angle.
>
>
> > I can send you off-list, if you want, the on-going script (incomplete,
> yet
> > well
> > documented I believe it to be).
> >
> > I would be happy to test your code and let you know the results. Let me
> know.
>
>
> Regards
>
> Sajid
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