[GRASS-user] calculating NDVI from i.landsat.toar

[Jiao Wang]

Forgot the link:
http://www.exelisvis.com/Home/NewsUpdates/TabId/170/ArtMID/735/ArticleID/13592/Digital-Number-Radiance-and-Reflectance.aspx


On Wed, Jul 2, 2014 at 8:59 AM, Jiao Wang <jiao at hawaii.edu> wrote:

> Hi Rajat,
>
> Surface reflectance should be used for calculating NDVI.
> Here is a link that explains the difference between radiance and surface
> reflectance.
>
> Best,
> Jiao
>
>
> On Tue, Jul 1, 2014 at 11:59 PM, Rajat Nayak <rajat27404 at gmail.com> wrote:
>
>> Dear All,
>> I am trying to calculate NDVI for my study area using landsat 8 products.
>> I calibrated images using i.landsat.toar. Now I'm a little confused.
>> If I use -r flag, I get radiance values at the sensor. If -r flag is not
>> used
>> I will get reflectance values.
>> Now the question is which one of the two,
>> radiance (obtained using -r flag) or surface reflectance (without any
>> flags)
>> should I use for calculating NDVI.
>> It will also be great if you can let me know the difference between the
>> two
>> and how it will influence my NDVI calculations.
>>
>> Thanking you
>> Regards
>> Rajat Nayak
>>
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>>
>
>
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