[GRASS-user] combining tiles

[Tyler Smith]

Hi,

I'm a brand-new Grass user. I'm working on an ecological niche
modelling project, for which I'm using the WorldClim bioclimatic
tiles. They are distributed as .bil files, which I've figure out how
to get into Grass. I need to convert them to ESRI ascii grid formats,
which I can also do.

My problem is that I need the data from parts of four separate
tiles. I've set up my location so that it will clip the appropriate
section as I export the grids into ascii format, but the only way I
can figure out to get the data into a single grid is to export each of
the four tiles separately, manually cut off the headers, import the
matrices into R, cbind() or rbind() them together, write.table them back
to a file, and then put the header back on. This works, but it's
tedious! 

There must be some Grass function to do this all in one step?
I've searched google and the on-line manuals with no luck, but
unfortunately I don't have access to the recommended published book
(waiting for the new edition before I buy it for myself).

Any help would be appreciated!

-- 
Regards,

Tyler Smith