[GRASS-user] Fwd: i.atcorr: Returns empty raster

[Sajid Pareeth]

Missed the list
---------- Forwarded message ----------
From: Abhishek Manandhar <abhishek.adams at gmail.com>
Date: Thu, Mar 17, 2016 at 1:38 PM
Subject: Re: [GRASS-user] i.atcorr: Returns empty raster
To: Sajid Pareeth <spareeth at gmail.com>


-I checked the region and it matches with the image's. I am totally
confused what exactly is making the problem. I got the Sentinel-2 Spectral
response curve from ESA, which I used to register new sensor. (If this
information might help)
-We can get quantification value from Level 1C product metadata. Besides
that, I have found many images with the mean values of whole scene above 12
bit range, generally snow covered areas. In the link below, the conversion
is explained where it says the default quantification value is 1000 . (
https://sentinel.esa.int/web/sentinel/technical-guides/sentinel-2-msi/level-1c/algorithm
)






On Thu, Mar 17, 2016 at 12:36 PM, Sajid Pareeth <spareeth at gmail.com> wrote:

>
>
> On Thu, Mar 17, 2016 at 12:12 PM, Abhishek Manandhar <
> abhishek.adams at gmail.com> wrote:
>
>> Hi,
>> Thanks for your reply.
>> -Empty raster file have NULL pixels.  But when I remove "-i" flag the
>> pixels are -nan. On both cases, the univar command returns nothing. Can you
>> assume, why it is happening?
>>
>
> Usually it happens when the region is not proper. Check your mapset
> projection and that of the data.
> Please post "g.region -p"
>
>
>> -Sentinel 2A data are captured in 12 bit but later converted to
>> reflectance (0-1) and is converted to integer with quantification value
>> 10000 (which used to be 1000 before). So the value ranges from 0-10000 at
>> current state.
>>
> I am not sure about this. I think quantification is done while converting
> from level 1C to level 2A  in their toolbox - SNAP. Do you have any source
> for this info?
>
> I have a similar sentinel band 2 (March) with data ranging from 0 to 22132
> but histogram shows the absurd high values are only single pixels and I
> dont know why they exists. 99 percent of the pixels are below 1500. If the
> quantification is done with 10000, i would expect much higher values spread
> over my histogram.
>
> to check the histogram:
> d.mon wx0
> d.histogram S2A....B02
>
>
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