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

[Niels Thevs]

Dear Yann chemin,

have many thanks for your detailed reply.

Currently, I have GRASS 6.2 in an Debian Environment. When I update to 
the version which includes i.albedo, which one should I choose, 
experimental stable or experimental unstable ?

Best regards

Niels


Yann Chemin schrieb:

> Dear Niels,
> 
> r.albedo is now i.albedo,  few days back it has been moved from
> AddonsSVN to mainSVN of GRASS.
> 
> I.evapo.potrad is the potential evapotranspiration from incoming sun
> radiation, meaning non-water stressed ET. It would be useless in areas
> where there is any water stress like a desert.
> 
> i.evapo.SENAY refers to a simple water stress estimation based on
> temperature from satellite. This has proven useful by Senay (2007)
> while mapping the whole of Afghanistan at once. We found limitations
> when dealing with small areas.
> 
> i.eb.evapfr is certainly going to push you further into water stress
> sensitivity anaylsis, but for that you'll need to use many GIPE
> modules, this is why there is a script_generator/ in GIPE directory,
> it will automatize the set up of all of the modules function into an
> easy script to perform several evapotranspiration mapping under
> various water stress estimation systems (various models are in GIPE:
> i.eb.h_SEBAL95/01, i.eb.h_iter, etc...). However, the script generator
> is not updated to the latest changes I had to make to integrate those
> GIPE modules into the main GRASS SVN. So you'll need to run the script
> generator, and then run the lines one by one to check the changes
> according to your set up. Once the GIPE modules are integrated into
> main GRASS, I'll update the script_generator.
> 
> i.dn2full.l5/7 generates top of atmosphere radiative temperature. You
> will still need to pull out a correction to get the radiative
> temperature corrected to skin surface temperature. In very clear and
> dry conditions, there should be very less correction to make.
> 
> Transmissivity of the atmosphere is an efficiency factor [0-1] that
> expresses the loss of radiation from 100% arriving at top of
> atmosphere. Single-way transmissivity, is a one-way ticket either from
> top of atmosphere to the skin surface of the Earth or from the skin
> surface of the Earth to the Top of Atmosphere. Try 0.7 for a start if
> you do not have cloudiness indices or Angstrom equation
> parameterization locally.
> 
> Cheers,
> Yann
> 
> 2008/9/29 Niels Thevs <thevs at uni-greifswald.de>:
> 
>>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
>>
>>-----------------------------------------------------
>>
>>
>>
> 
> 
> 
> 

-- 



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

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