[R-sig-Geo] conservative continental "reprojection" for lon-lat input?

[Chris English]

Tom,

Link to advice from Tomislav Hengl
http://grokbase.com/p/r/r-sig-geo/1226xdq5sh/help-to-analisys-spatio-temporal 

expresses preference for gstat but suggests Stem
might do the trick by design

http://cran.r-project.org/web/packages/Stem/ 

Model accepts UTMx, UTMy or LAt/LON coords(Stem.pdf, Stem.Model(...))

Not sure that this will help, but as you can spell
Eulerian you've a better grasp of the problem contemplated.

Hope this is both relevant and helps,
Chris

> From: Tom_Roche at pobox.com
> To: r-sig-geo at r-project.org
> Date: Wed, 7 Nov 2012 14:08:32 -0500
> Subject: [R-sig-Geo] conservative continental "reprojection" for lon-lat	input?
> 
> 
> http://cran.r-project.org/web/packages/gstat/vignettes/gstat.pdf
> > Package gstat assumes that data are projected, i.e.
> > [data] should not be provided as [latitude]/longitude.
> 
> How should a continental-scale reboxing project best cope with this
> restriction? Why I ask:
> 
> I'm a student attempting to create 3D N2O initial conditions (ICs) and
> boundary conditions (BCs) for a run of an Eulerian atmospheric model
> over North America, specifically
> 
> https://github.com/TomRoche/cornbeltN2O/wiki/AQMEII-North-American-domain#wiki-EPA
> > projection: LCC (Lambert Conformal Conic)
> > standard parallels: 33°, 45° (N)
> > lon/lat projection center: -97° (W), 40° (N)
> > domain origin (from projection center, in km): -2556 (W), -1728 (S)
> > horizontal grid spacing: 12 km
> > horizontal grid count (x,y): 459, 299
> > vertical grid count: 34
> > max height: 50 mb
> 
> I'm attempting to create IC/BCs for my model using, as input, the output
> of a more coarse-scaled 3D global inventory: 2.5° lon x 1.875° lat, with
> vertical layer heights more resembling those of the output domain
> (though the layer positions differ). This "global input" provides an
> approximate value for the mass concentration of N2O in the air in each
> of its voxels, or boxes.
> 
> So I'll need to "rebox" the global input onto the local domain: i.e.,
> for each box in the North American projected domain (i.e., for the
> "local output"), estimate its mass concentration based on those provided
> for the global input. I was hoping to do this directly, in the manner
> that raster::projectRaster allows one to "regrid" from lon-lat to LCC.
> But direct reboxing from lon-lat appear problematic with package=gstat,
> however. Am I missing something?
> 
> If not, I'm wondering: what would be the most safe, conservative way to
> impose a projection on the global data in order to input it to gstat?
> E.g., could I
> 
> 1. reduce the extent of the input from global to a "subglobal" area
>    somewhat larger than my target domain (which is -130 - -59.5° lon,
>    23.5 - 58.5° lat)
> 
> 2. impose some CRS on the subglobal data such that the areas of the CRS
>    gridcells equal or closely approximate those of the subglobal grid.
> 
> ? If so, which CRS to use?
> 
> TIA, Tom Roche <Tom_Roche at pobox.com>
> 
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