[gradsusr] evaluation of grads expressions in pygrads (galab.py)

[Francesco Benincasa]

I forgot the two images, sorry.

* lunedì 28 novembre 2011, alle 13:08, Francesco Benincasa scrive:
> * venerdì 25 novembre 2011, alle 12:20, Arlindo da Silva scrive:
> [...]
> > Can you give us some more details here? Is this a global or regional dataset?
> 
> It's a regional dataset.
> 
> > Also, which version of pygrasd is this? Platform?
>   
> pygrads 1.1.4
> python 2.6.5
> OS OpenSuSE 11.3
>  
> >     and I've noticed that
> >     in some cases the map is drawn correctly only if I use the "transf"
> >     option set to True (the projection is cylindric).
> > 
> > In principle, you should not have to set the "transf" attribute. This is an
> > internal parameter to signal the package that a map transformation is
> > necessary, "under the hood" kind of stuff.
> [...]
> > Here is the main issue that drives this special handling. GrADS is very
> > flexlible in its addressing of longitudes: [-180,180],  [0,360], [20,380], all
> > is fair game. The Basemap toolkit (and the proj4 library it relies on) less so,
> > it wants longitudes in the range [-180,180]. Therefore, anytime a map
> > transformation is necessary the longitude domain of the input grid get changed
> > to the range [-180,180], a map transform is applied, and the the original grid
> > arrangement is restored after the transform.
> 
> Ah ok, thank you for your explanation.
>  
> >   I am not exactly clear what your particular problem is. If you send me a
> > small sample file I can try it out and fix whatever bugs may be in there. I
> > always work with global files, so it is possible that I may have overlooked
> > some important detail for regional files (if indeed you have a regional file).
> 
> I attach two images, one with the map correctly drawn (with the "transf"
> optino set to True) and one with the wrong one. You can download a test
> dataset from here:
> http://sds-was.aemet.es/archive/files/testfile.nc
> 
> I use some different dataset from various models (both global and regional)
> and I only have to set the transf option with this model.
> 
> Thank you very much.
 
-- 
| Francesco Benincasa
| http://www.linkedin.com/in/fbenincasa
****
Civilization is the limitless multiplication of unnecessary necessities.
        -- Mark Twain
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