[R-sig-Geo] Reading National Snow and Ice Data Center binary files

[Roger Bivand]

On Wed, 19 Oct 2011, Anthony Fischbach wrote:

> Thank you for the GRASS suggestion.
> It would also be straight forward in ArgGIS, but I seek to run this all in a
> scripting environment with the full flexibility of R such that I may
> automate the whole process.

I have a feeling that this is stranding on the raster warping difficulty 
seen in high latitudes. The projected cells have great difficulty in 
"adapting" to longlat, for obvious reasons, as the output cells really 
need to differ in shape and form. Would it be possible to "go vector" 
instead, and project the vector entities? I have some slides from a course 
I gave three years ago but I'm not sure if they are relevant.

Roger

>
> Following on the projectRaster idea, I have tried using the from and to
> options, first creating a from raster corresponding to the geographic extent
> and resolution of the desired output raster.
>
>> ll_lt <- 30.98
>> ll_ln <- 168.35
>> ur_lt <- 33.92
>> ur_ln <- 279.26
>> rGeo <- raster(nrows=448, ncols=304, xmn=ll_ln, xmx=ur_ln, ymn=ll_lt,
>> ymx=ur_lt, crs="+proj=longlat +datum=WGS84")
>> ## look at the raster before projecting
>> rr
> class       : RasterLayer
> dimensions  : 448, 304, 136192  (nrow, ncol, ncell)
> resolution  : 25000, 25000  (x, y)
> extent      : -3837500, 3762500, -5362500, 5837500  (xmin, xmax, ymin, ymax)
> coord. ref. : +proj=stere +lat_0=90 +lat_ts=70 +lon_0=-45 +k=1 +x_0=0 +y_0=0
> +a=6378273 +b=6356889.449 +units=m +no_defs
> values      : ...\SeaIce\NSIDC\NearRealTime\nt_20111011.tif
> min value   : 0
> max value   : 1
>> ## Project
>> rgeo <- projectRaster(from=rr, to=rGeo, method= 'bilinear')
>> rgeo
> class       : RasterLayer
> dimensions  : 448, 304, 136192  (nrow, ncol, ncell)
> resolution  : 0.3648355, 0.0065625  (x, y)
> extent      : 168.35, 279.26, 30.98, 33.92  (xmin, xmax, ymin, ymax)
> coord. ref. : +proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0
> values      : in memory
> min value   : 0
> max value   : 0
>
> It fails to populate with the data.
>
> -----
> Tony Fischbach, Wildlife Biologist
> Walrus Research Program
> Alaska Science Center
> U.S. Geological Survey
> 4210 University Drive
> Anchorage, AK 99508-4650
>
> AFischbach at usgs.gov
> http://alaska.usgs.gov/science/biology/walrus
> --
> View this message in context: http://r-sig-geo.2731867.n2.nabble.com/Reading-National-Snow-and-Ice-Data-Center-binary-files-tp6882737p6909785.html
> Sent from the R-sig-geo mailing list archive at Nabble.com.
>
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-- 
Roger Bivand
Department of Economics, NHH Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no