[GRASS-user] NDVI analyses with Landsat 8

[Huub Munstege]

Dear all,

in the following link I've uploaded an image that gives a bit more context information:

http://www.flickr.com/photos/hmunstege/9036837366/

The problem boils down to the different wavelength range of the the NIR band of Landsat 8. It's much narrower and applying the ndvi tools from Landsat 7 doesn't give a clear image (see the image).
I am not a remote sensing expert, but we use frequently the ndvi index to monitor the exploitation of rice schemes along the Niger river in Mali. We would love to incorporate the Landsat 8 images in our analyses (without the 'nodata scratches' of Landsat 7!)

Thanks in advance for your attention.


 

________________________________
Huub Munstege
BPE 2836
Bamako, Rep. du Mali
Tel:      +223 20226397
Port:     +223 78370695 
________________________________



>________________________________
> De : Nikos Alexandris <nik at nikosalexandris.net>
>À : Huub Munstege <hmunstege at yahoo.com> 
>Cc : "grass-user at lists.osgeo.org" <grass-user at lists.osgeo.org> 
>Envoyé le : Mercredi 12 juin 2013 21h58
>Objet : Re: [GRASS-user] NDVI analyses with Landsat 8
> 
>
>Huub Munstege wrote:
>
>> Hello Nikos,
>
>Hello Huub!
>
>> thx for the swift reply. I'll check out the options you mentioned but at
>> first sight I noticed that 'i.vi' tool is not available for me ( I'am on
>> 6.4.3-rc, from the AUR package in Archlinux). I.vi is not a command in the
>> 'standard' Grass trunk. Neither is it available as an add-on.
>
>Right!  Apologies from my side.  I have a setup giving access to all grass 
>modules outside of a grass session [see link to GRASS-Wiki below] which, if 
>not properly handled, as described in the wiki ("strip paths"), it even allows 
>access to all grass70 modules from inside a grass64 session.
>
>> Some more explanation as you asked: previous Landsat 7 images we analyzed
>> with a simple raster calculation with the following formula:
>> float(Band-4 - Band-3) / (Band-4 + Band-3).
>
>I guess using grass64 means sticking to the formula above for NDVI.
>
>> But as you already noticed the bands and ranges have changed under Landsat
>> 8. Various combinations of bands (4,5 and 8) give a result that is at best
>> not so clear cut as the analysis done with L-7.
>
>I didn't test any L8 so far, though I have downloaded some scenes.  Strange, 
>in a way -- I would rather think that their improvements would improve S-N-R 
>and, thus, derive "better" vegetation indices... :-?
>
>> The "bluntly subtraction with 0.12" is based on on a quick scan of the
>> obtained result. Areas without vegetation in our project area should give
>> values in the range between -0.05 - 0.
>
>as per L7 data I guess...
>
>> The result of the combination of the 5 and 4 bands in the above formula 
>> gives values that are aprroximately 0.12 higher.
>
>I see.  
>
>> Therefore the blunt and in-elegant subtraction which is definitely wrong.
>> But it gives us for the time being a better deistinction between cultivated
>> irrigation schemes and their surroundings. Maybe I am simply too impatient
>> and too eager to work with the new fresh data from L-8.
>
>Sorry for asking again:  did you correct the data in some way or did you 
>simply feed the formula with DNs?
>
>> Undoubtedly soon, Grass and the other software will incorporate specific
>> modules that will be tailored to the L-8 sensors.
>> Cheers and keep up the good work,
>
>Thank you for all of the details regarding your work.
>
>Nikos
>---
>
>
><http://grasswiki.osgeo.org/wiki/Working_with_GRASS_without_starting_it_explicitly#Bash_examples_.28GNU.2FLinux.29>
>
>
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