Steven,

In principle you could give merge all tiles (e.g. make a list of RasterLayer
objects and use do.call ) but merge is quite slow (something that can easily
be be improved; and I expect it will be over the coming months).

What I would do is use run gdalbuildvrt (that comes with the FWtools). This
creates a single header file that lets you access all the tiles as a single
virtual file. If you want a single file for better performance, you can use
writeRaster to save it to e.g. a single geotiff file.

Robert


On Sun, Oct 16, 2011 at 8:54 PM, steven mosher <moshersteven@gmail.com>wrote:

>  I have 72 "tiles" in a tif format and each tile is   30X30
>
> >tile
> class       : RasterLayer
> dimensions  : 3600, 3600, 12960000  (nrow, ncol, ncell)
> resolution  : 0.008333333, 0.008333333  (x, y)
> extent      : 60, 90, 60, 90  (xmin, xmax, ymin, ymax)
> coord. ref. : NA
> values      : C:/Users/steve/....
> min value   : 0
> max value   : 255
>
> What I'd like to do is find  the fastest way to bring all 72 tiles
> into one big raster.
>
> merge() seems like one good choice, where I would   merge each tile
> with a blank raster that would get
> filled in incrementally by each tile
>
> > world
> class       : RasterLayer
> dimensions  : 21600, 43200, 933120000  (nrow, ncol, ncell)
> resolution  : 0.008333333, 0.008333333  (x, y)
> extent      : -180, 180, -90, 90  (xmin, xmax, ymin, ymax)
> coord. ref. : +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs
> +towgs84=0,0,0
> values      : none
>
> world <- merge(tile, world)
>
> and the  repeat that for the remaining 71 tiles.  I'm also think that
> one could extract the values from the tile
> and use setValues  but  that appears to hit the memory wall in
> Windows.  The other option
> I suppose is to use writeValues()  and create  a big file from the tiles.
>
> Am I missing any obvious options?
>
> Steve
>
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