[Qgis-user] Using/visualizing 3D data (Z values)

[Paul Lens]

Hi all,

1. I made a TIN surface, using the interpolation plugin, from a point 
shapefile (with "ALTITUDE" field) and  3D line shapefiles. I lost time 
trying to extract the relevant lines from the line shapefiles without 
loosing the 3D information (Z values of the nodes).
If I remember well, I first used "Merge Layers" from the mmqgis plugin, 
and it kept the Z information. Than, I used the Intersection command in 
the Vector menu, and the Z information was lost. Finally, after manually 
selecting the relevant lines and using "save as", I got the expected 3D 
line shapefile keeping the Z values.
Is this loss of Z information a known limitation of the gdal vector 
commands in QGIS (vector menu) and is this limitation affecting all 
these commands? Or did I do something wrong?

2. In a second step, I wanted to be able to easily see (through labeling 
a Z field) or ask (with the identify command) those Z values from the 3D 
lines, so as to fine tune the interpretation of the topography.
Again the gdal tool (in Vector menu) "Node Extraction" lost all Z 
information.
Is there a workaround to create a point shapefile with a Z field? Or, at 
least, to keep the Z values in a point shapefile, rasterize it so as to 
be able to visualize the Z value using  the "Identify" command on the 
raster?

Thanking all the developers for this wonderful program,

-- 
Paul