Converting a .dxf to a .shp containing a field with height information in QGIS?

Question

I received two .dxf for my project that represent my area of interest: one of them contains buildings, the other one terrain elevation (they both are 3D). I can successfully convert them to shapefiles using the Dxf2Shp plugin. They also display nicely compare to sample below:

However, I loose the height information if I do so. The only field I get in the attribute table is "myid", that simply counts the polygons. Is there a way to convert the files to .shp creating a height field in the attribute tables, that takes the z values from the .dxf? This would already be fine, as the projection is metric.

Answer 1

You can try the GRASS command v.in.dxf in Processing or in the Grass plugin (look at GRASS GIS: import DXF).

Some results in GRASS GIS with 3D dxf files:

• from Vector support in GRASS GIS: Möbius strip visualization to show the 3D vector capabilities of GRASS 6 - imported from 3D DXF (screenshot: M. Neteler)

• or geological layers (3D dxf) (my work from Grass Gis et Paraview: la modélisation géologique 3D pour les démunis, ou les enthousiastes...)

The problem is that there is no support for 3D in QGIS: you must use Python with a module that support 3D (ogr or shapely), look at QGIS user: Using/visualizing 3D data (Z values) and QGIS user: visualizing 3D data (Z values) or data with z attribute: a solution or use the commands of GRASS GIS.

Answer 2

Since 2.14 Qgis supports 3d features. After importing DXF you can add height field with field calculator using expression:

z($geometry)

or

geom_to_wkt($geometry)

to get Well-Known Text (WKT) representation of the geometry.