I am working on several autocad polylines (with several vertices...) that have the exact N,E coords but now I would like to add the elevation data for every polyline's vertices from a dtm.

I thought it was an easy task but I can't reach my goal so far.

I imported dxf polyline in QGIS (I tried also in GRASS).

There it seems that v.drape doesn't work.

In fact, I exported the vector as dxf (with flag -z) but I have all vertices at a same elevation (find from centroid in dtm) and the result is "flat" polylines at different elevation which is no good.

I would like to have each of the polyline's vertices with a different elevation.

Is there a way to do an easy thing like this?

I want to transform a 2d dxf in a 3d dxf by draping it on a dtm.

2 Answers 2


Ok, I solved. I use Global Mapper instead of GRASS or QGis. There is an option to add elevation data to all vertices from the dtm. Then I exported the vector as a dxf. I still have in Autocad a 3D DXF. Great and easy! :)


You can use v.what.rast to transfer raster map values to vector nodes. If you need more nodes, use v.split beforehand.

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