I've built my own DFF 3D printer and have played with a variety of stl programs.

Openscad can be used to intersect your surface with a cube to generate a printable stl file. It still might have to be run through something like netfabb to cleanup the stl.

Also there are mesh processing libraries for the processing.org software that could create an stl.

http://landprint.com/ is one company that provides a commercial service for land data, I assume that they could also work with your bathemetry.

If the data is a pure X/Y grid with one Z value per X/Y pair, it should be straightforward to write software to turn it into an stl file. PM me if interested.

-Rob A>



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