Color equalization after patching/mosaicking the satellite data from multiple scenes

[Sajid Pareeth-2]

Hi all

I have some data from different scenes of Landsat8 covering my area of interest. But after mosaicking, it clearly shows the border line and the difference in colors in the composites.

For example I am attaching two cases, one from Sentinel2 and another from Landsat8.

I mosaicked two scenes of sentinel taken on the same day,- November 19 2016, and tried following commands to get a composite.

i.colors.enhance blue=S2A_B02 green=S2A_B8A.hpf red=S2A_B11.hpf
r.composite blue=S2A_B02.hpf green=S2A_B8A.hpf red=S2A_B11 output=test_118A02

And it works perfect, there is no sign that the image is from two scenes (attached - S2_19Nov2016comp_118A02.jpg ).

But in the case of L8, it is more complicated as the data is coming from three scenes. Two scenes are from the same orbit and third from adjacent which has a different date.
For each  scene, there are two acquisitions in November 2016 (Total six images in November 2016 for this g.region).
Hence I used r.patch and r.series to create a November month composite and with this, the color composite looks really bad.

i.colors.enhance blue=L8_B02.hpf green=L8_B05.hpf red=L8_B06.hpf
r.composite blue=L8_B02.hpf green=L8_B05.hpf red=L8_B06.hpf output=test_652

Please see attached "L8_Nov2016_comp_652.jpg"

Is there anything I miss here to obtain a good composite over multiple scenes taken from different dates, but from the same month?

Regards

Sajid

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[NikosAlexandris]

* Sajid Pareeth <[hidden email]> [2016-12-30 16:34:23 +0100]:

>Hi all
>
>I have some data from different scenes of Landsat8 covering my area of
>interest. But after mosaicking, it clearly shows the border line and the
>difference in colors in the composites.

Dear Sajid,

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).

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).

Cheers, Nikos


ps-  We need more advanced algorithms for such tasks (ie relative
radiomatric normalisation).

>For example I am attaching two cases, one from *Sentinel2* and another from
>*Landsat8*.
>
>I mosaicked two scenes of sentinel taken on the *same day,- November 19
>2016*, and tried following commands to get a composite.
>
>i.colors.enhance blue=S2A_B02 green=S2A_B8A.hpf red=S2A_B11.hpf
>> r.composite blue=S2A_B02.hpf green=S2A_B8A.hpf red=S2A_B11
>> output=test_118A02
>>
>
>And it works perfect, there is no sign that the image is from two scenes
>(attached - S2_19Nov2016comp_118A02.jpg ).
>
>But in the case of L8, it is more complicated as the data is coming from
>three scenes. Two scenes are from the same orbit and third from adjacent
>which has a different date.
>For each  scene, there are two acquisitions in November 2016 (Total six
>images in November 2016 for this g.region).
>Hence I used r.patch and r.series to create a November month composite and
>with this, the color composite looks really bad.
>
>i.colors.enhance blue=L8_B02.hpf green=L8_B05.hpf red=L8_B06.hpf
>> r.composite blue=L8_B02.hpf green=L8_B05.hpf red=L8_B06.hpf output=test_652
>>
>
>Please see attached "L8_Nov2016_comp_652.jpg"
>
>Is there anything I miss here to obtain a good composite over multiple
>scenes taken from different dates, but from the same month?
>
>
>Regards
>
>Sajid

>_______________________________________________
>grass-user mailing list
>[hidden email]
>http://lists.osgeo.org/mailman/listinfo/grass-user


--
Nikos Alexandris | Remote Sensing & Geomatics
GPG Key Fingerprint 6F9D4506F3CA28380974D31A9053534B693C4FB3
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[Sajid Pareeth-2]

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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[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 <[hidden email]>
To: Nikos Alexandris <[hidden email]>
Cc: GRASS user list <[hidden email]>
Subject: Re: [GRASS-user] Color equalization after patching/mosaicking
        the satellite data from multiple scenes
Message-ID:
        <[hidden email]>
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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