Building a buffer over a terrain model

Question

I have a polygon and a terrain model (can be either grid or TIN). I'd like to a build, say, a 1km buffer so that the 1km is measured over the surface of the terrain, i.e. not planimetric. The buffer must always be at least 1km from the polygon and prefer a measure over the flattest part of the terrain.

Anyone know a good way to do this that is robust for all the edge cases you get with real terrain?

An algorithm or solution using FOSS tools is preferred.

Answer 1

with Grass Gis it's posible look this link

http://grass.ibiblio.org/gdp/html_grass62/r.buffer.html

or with pgraster

http://trac.osgeo.org/postgis/wiki/WKTRasterTutorial01

http://cartosig.upv.es/es/system/files/jomarlla/PGRASTER_20070710-0001.pdf

good luck