[GRASS-user] add ons i.evapo.potrad, senay

[Niels Thevs]

Dear Yann Chemin,

have many thanks for your reply regarding i.dn2full.l5/17:

The background of my question was that we want to calculate 
evapotranspiration from desert and semi desert areas. According to your 
and other users' experience, which add on performs better: 
i.evapo.potrad, i.evapo.senay, or i.eb.evapfr ?

Regarding the required input parameter for i.evapo.potrad and 
i.evapo.senay, can I use r.albedo and where do I find it ? Can I derive 
the surface skin temperature through i.dn2full.l5/17 ? I was wundering 
because in the description for i.dn2full.l5/17 there was written that DN 
is calculated into radiance at top of the athmosphere. Furthermore, what 
is the single way transmissivity ?

Best regards

Niels




Yann Chemin schrieb:

> Hi Niels,
> 
> in grass-Addons/gipe/ there are a couple of functions to get L1b
> Landsat 5/7 into radiant temperature at top of atmosphere.
> 
> i.dn2full.l5
> i.dn2full.l7
> 
> this corrects standard images having .met standard metadata file or
> NLAPS metadata (.txt) file.
> 
> You may try and see if you get to some useful ends.
> 
> You may also see some fast method to get surface temperature from this
> product by using emissivity. As it was used for AVHRR 15 years ago.
> 
> 
> in Grass-Addons, i.landsat.toar may also help you out, but it is a
> long time I have had a look at it.
> 
> Cheers,
> Yann
> 
> 2008/9/25 Niels Thevs <thevs at uni-greifswald.de>:
> 
>>Dear Grass users,
>>
>>does anybody have experience with the calibration of the Landsat thermal
>>data ? I have a few ground measurements of temperature (air temperature in 2
>>m above surface) and want to relate them to a corresponding Landsat image
>>(band 6). In the papers which I read there are listed a lot of working steps
>>like calibration for at sensor radiance, surface radiance, etc. Is it
>>necessary to do all those steps or does anybody know a more simple algorithm
>>?
>>
>>Best regards
>>
>>Niels
>>
>>--
>>
>>
>>
>>-----------------------------------------------------
>>Dr. Niels Thevs
>>Chair of Geobotany and Landscape Ecology
>>Institute of Botany and Landscape Ecology
>>Greifswald University
>>Grimmer Strasse 88
>>17487 Greifswald
>>Germany
>>
>>Tel.: +49-3834-86-4137
>>Fax:  +49-3834-86-4114
>>
>>-----------------------------------------------------
>>
>>
>>
>>_______________________________________________
>>grass-user mailing list
>>grass-user at lists.osgeo.org
>>http://lists.osgeo.org/mailman/listinfo/grass-user
>>
> 
> 
> 
> 

-- 



-----------------------------------------------------
Dr. Niels Thevs
Chair of Geobotany and Landscape Ecology
Institute of Botany and Landscape Ecology
Greifswald University
Grimmer Strasse 88
17487 Greifswald
Germany

Tel.: +49-3834-86-4137
Fax:  +49-3834-86-4114

-----------------------------------------------------