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GLOBE

GLOBE is short for Global Land One-km Base Elevation Project. It is a Digital Elevation Model (DEM).

Coverage:
that covers the complete land surface in a resolution of 30 arc seconds, which is twice as high as ETOPO.
License:
Most of the data is copyright-free. However, the authors expect to be cited. See here for further information.
Author:
See here.

Download

http://www.ngdc.noaa.gov/mgg/topo/gltiles.html

Conversion to xyz format

The data is given in gridded binary files, with the elevation stored as 16-bit signed integer numbers.

These files can be converted to the GMT *.grd format as follows:

xyz2grd a10g -Ggrid.grd -R-180/-90/50/90 -I30c -N-9999 -V -F -ZTLh

In order to convert all files at once (in the bash shell):

FILES=(*10g)
LAT_S=(50 0 -50 -90)
LAT_N=(90 50 0 -50)
for((y=0; y<=3; y++)); do
    for(( x=0; x<=3; x++)); do
        REGION="$((-180+$x*90))/$((-90+$x*90))/${LAT_S[$y]}/${LAT_N[$y]}"
        xyz2grd ${FILES[$(($y*4+$x))]} -G${files[$(($y*3+$x))]}.grd -R$REGION -I30c -N-9999 -V -F -ZTLh
    done
done

Then, to get a global xyz file:

{ for i in *.grd; do grd2xyz $i; done; } | sort -k2nr -k1n > globe.xyz

 Conversion to GMT grd

 xyz2grd GLOBE.xyz -Rd -F -GGLOBE.grd -I30c
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