Downsampling of Topographic Data

This can be done using the following script: downsample-gmt.sh

Examples:

./downsample-gmt.sh etopo1.xyz > output.xyz
./downsample-gmt.sh etopo1.grd > output.xyz

It uses GMT's grdsample program; for that, it converts the data into the *.grd format (or omits that step if a grid file is given). For the conversion to *.grd a gridspacing of 1 arc minute is assumed (= like ETOPO1).